Comments

  • My own (personal) beef with the real numbers
    It appears like we need to go back over the law of identity, and the difference between identical and equal. Remember, I don't accept set theory on the basis that it violates the law of identity, so why give me a proof based in a set?Metaphysician Undercover

    You want to make a mathematical claim (sqrt 2 doesn't exist) but you won't accept a mathematical response. Makes for pointless conversation.

    I don't accept set theory on the basis that it violates the law of identityMetaphysician Undercover

    I have already explained to you at length that set theory is based on the law of identity; and that the mathematical equals sign expresses identity between two expressions.
  • My own (personal) beef with the real numbers
    The square root of two just won a Golden Globe award!jgill

    LOL
  • My own (personal) beef with the real numbers
    The construction procedure you described is never ending, just like the never ending digits.Metaphysician Undercover

    No, you're thinking of something else. I'm talking about the algebraic construction. Which I'll outline.

    * Say you believe in the rationals. You believe in the rationals? Ok.

    * Now arbitrarily make up a symbol, call it , but bear in mind that this is an entirely arbitrary symbol that has no meaning. It's just some squiggles I type in.

    * Now consider the set of all formal expressions . Again, these are just marks on paper. They have no meaning.

    * We can define "addition" on these expressions componentwise. So



    * Likewise we can define the "product" of two such expressions using the everyday distributive laws. FOIL if you learned that awful acronym designed to replace understanding with mindless drudgery. God I hate what passes for math education. My friend @Meta your mathematical ignorance is not your fault. I blame your teachers and the textbook committees and the educrats of your high school years.

    * Now the set happens to have a mathematical structure identical to that of the rationals; and in addition, it contains a square root of 2.

    * If one then objects that these are "only formal symbols," well after all what are rational numbers but formal symbols that obey rules? And in fact we can go further and construct, out of bits and pieces of set theory, a mathematical structure that is the set-theoretic implementation of this set of symbols.

    Fact: If you believe in the rationals, you must believe in the rationals augmented by the square root of 2.

    You want to make some kind of distinction that the "rationals are actual" in some sense. But they're not. They're just as fictional.

    ps -- You make a mathematical claim, "Sqrt 2 doesn't exist." Then you reject any mathematical counterargument. You can't lose that way, but you can't convince anyone else.

    If you are going to make a mathematical claim you need to be able to accept a mathematical disagreement.
  • My own (personal) beef with the real numbers
    The problem is that you do not address the substance of the argument. You go off on some tangent using mathematical jargon, without addressing the issue.Metaphysician Undercover

    I could respond but what would be the point? It is a logical truth that IF you believe in the rational numbers then you must necessarily believe in the rational numbers augmented by the square root of 2. It's a simple logical procedure to go from one to the other. You want to complain that this is a sophisticated mathematical argument. Actually it is. But I've just explained it in a most understandable way. You needn't follow the details of the procedure. What matters is that there is one. You can literally build a square root of 2 out of the rational numbers. I have in fact outlined the procedure a couple of times already.

    I can't expect you to follow mathematical arguments. I am simply making you aware of the existence of these arguments.

    Your preference not to engage with mathematical arguments does not give you the right to deny that such arguments exist. You don't have to follow the algebraic details. You do have to understand that from the standpoint of pure logic, the correctness of the rationals implies the correctness of a number system that includes the rational augmented with the square root of 2.

    Else you really are trying to use ignorance as a weapon. "I don't understand it so don't waste your time explaining it to me," is acceptable if lame. But "I don't understand it therefore it's false," I hope you can see is not a sensible argument at all.
  • My own (personal) beef with the real numbers
    Fishfry! Get with the program, wake up and smell the coffee!Metaphysician Undercover

    I love coffee. My favorite part of the day is my morning coffee. I can't wait to wake up tomorrow morning and smell the coffee. Often I grind my fresh artisinal beans and then bring the container to my nose, inhaling the aroma. Ah, coffee. Nectar of the Gods.

    I hope you will not mind too much if I refrain from commenting on other topics. If I said anything it could only be what I've said before. Little would be gained in further punishing the keys of my laptop.

    it's pointless to speak sophisticated math at me.Metaphysician Undercover

    Ignorance as a debating point. "Your argument stands refuted because I'm incapable of understanding it." I can't top that.
  • Universe as simulation and how to simulate qualia
    Computers can simulate physical systems. Human brains are physical systems. Human brains are conscious. So a simulation of a human brain will be consciousPfhorrest

    A simulation of gravity doesn't attract nearby bowling balls. A simulation of the brain would perfectly simulate the behavior of a brain but would not necessarily implement consciousness.

    Is there something spooky about wetware? We don't know. That's Searle's argument I believe. Something special about the wetware.

    By definition a simulation is an "imitation"ZhouBoTong

    Exactly right. If the world is a simulation, what's it a simulation of??
  • Circular Time Revisited
    This is an argument that we will experience identical lives over and over againDevans99

    I don't want to do that. I want the opportunity to do better in the next life. It would be awful to live the same life over and over.

    This by the way is an objection to the idea of uploading your mind to a computer (something I don't personally believe will ever happen). Any computer is finite. You would eventually start duplicating states. You would in fact be condemned to live the same life, over and over. You would beg your technicians to stop your program.

    In the future, being uploaded to a computer and forced to live the same life, over and over and over forever, will be a punishment administered to the worst offenders. Being condemned to live forever would be literally a fate worse than death. There's a sci-fi story in there if someone wants to write it.

    For that matter see the Anne Rice vampire novels. At first eternal life seems like a gift. In the end it turns into a nihilistic horror.
  • What is the difference between actual infinity and potential infinity?
    The square root of two is rational? Am I misreading your sentence?/quote]

    Oh that's a typo, sorry. Is that what you were asking earlier? Yes typo of course. I'll go back and fix it.
    jgill
  • If Climate Change Is A Lie, Is It Still Worth The Risk?
    It doesn't matter if climate change is a complete lie! The obvious move is to cover your ass anyway!Lif3r

    Isn't that Pascal's wager? If God exists, a little piety, showing up to church on Sunday, being kind to your fellow man, are a small price to pay for eternal salvation. And if you don't do those things but God does exist, you'll receive eternal damnation. Like spending eternity on hold with the insurance company as I was a little while ago. If God exists, the payoff for being pious is positive infinity; and the punishment for not being pious is negative infinity. If God doesn't exist, it only costs a finite amount of work to be pious. So by mathematical expectation, we should be pious whether or not God exists.

    Of course the assumption is that the creator of the universe is so petty as to sort his creations into "naughty" and "nice." This conflates God with Santa Claus. So I think it's not really a good argument. A God that's keeping track of your every move, every act, every naughty thought. This is the God of a highly neurotic culture I think.

    Re climate change, I favor a more nuanced approach.

    * Is climate change real, and is it any different lately than the normal variance you'd expect over the ages the earth has had a climate?

    * If there is a change and it's uniformly in one direction, is the cause primarily man-made?

    * Even if it is, are there any sensible actions we can take while preserving our economy?

    * How do we balance all these factors? We don't want to move back to caves and we'd like to be good stewards of nature. Where's the balance?

    * How's the science. Are computer models "truth?" The earth is billions of years old and our climate records mere hundreds, if that. Maybe there's a lot about the climate we don't know.

    Of course now I'm a "climate denier" and Sean Hannity as someone called me in another thread where I didn't even mention climate change!

    I do oppose climate hysteria. The bushfires in Australia are mostly due to arsonists. 183 people have already been arrested. That doesn't prevent the screeching of radical environmentalists.

    I think a sense of proportion, judgment, and thoughtful weighing of the evidence and alternatives and choices to be made, is better than hysterical panic that labels everyone who disagrees a hater and a denier. Having that opinion makes me in some people's eyes a hater and denier. It's frustrating but that's the culture these days.
  • My own (personal) beef with the real numbers
    OK, so we agree that if so-called "mathematical objects" are things which can be measured, Euclidian geometry creates distances which cannot be measured by that system. That agreement is a good starting point.Metaphysician Undercover

    You're a funny guy.

    You: The moon is made of green cheese.

    Me: Actually scientists think it's made of dirt and rocks and stuff.

    You: Ok good, now that we agree the moon's made of green cheese ...

    Man why you do me like this?

    OK, so we agree that if so-called "mathematical objects" are things which can be measured,Metaphysician Undercover

    No. There are nonmeasurable sets. Some mathematical objects can be measured and some can't. I would never say that "a mathematical object is a thing that can be measured" since that's false, meaningless, and misleading. You just made it up and decided that I said it. You keep doing this. Why?


    Euclidian geometry creates distances which cannot be measured by that system.Metaphysician Undercover

    I've told you half a dozen times already that:

    * The length of the diagonal is the Euclidean distance between the points (0,0) and (1,1), which is . We can define this via a metric, which is what I just did. We can also define it in terms of measure theory. I gave the links to those subjects earlier.

    You're hung up on the infinite decimal business but I've explained to you repeatedly that:

    * The fact that the decimal representation of a number is infinite, tells us nothing about whether the number itself is essentially a finitary or infinitary object. For example 1/3 = .333... has an infinite decimal expression but it can be summarized as "a decimal point followed by all threes." That's a recipe to produce a arbitrary number of decimal digits of 1/3. Likewise there is a recipe to product the decimal digits of ; as well as a recipe to produce the decimal digits of .

    * is computable; it has a finitely expressible continued fraction representation; and it lives in a finite extension of the rational numbers if one is an algebraist and doesn't like limits and infinite series. By these criteria, is a finitary object.

    * You keep clinging to your mistaken belief, thinking that the rational numbers are good and the irrationals bad. This is a personal psychological condition that can be remedied with mathematical knowledge. If you so desire.



    As a philosopher, doesn't the question, or wonderment, occur to you, of why we would create a geometrical system which does such a thing?Metaphysician Undercover

    LOL. My wonderment is that you consistently fail to engage with anything I say; repeatedly claim I said the opposite of what I actually said; and stubbornly cling to your misunderstood fractured math from high school.

    You say "such a thing" as if is beyond the pale, whereas rational numbers are wonderful. You just made this up. Both classes of numbers are equally fake or equally real, depending on how you look at it. You don't want to engage with this point, go in peace then. I can't do any more for you.

    That geometrical system is causing us problems, inability to measure things, by creating distances which it cannot measure.Metaphysician Undercover

    You keep repeating this without engaging with the fact that math says you're wrong. You keep repeating this over and over and over. I can't say anything beyond what I've already said many times.


    Maybe we can take this as another point of agreement. A "mathematical object" is nothing other than what you called a "funny gadget". Let's simplify this and call it a "mental tool". Do you agree that tools are not judged for truth or falsity, they are judged as "good" in relation to many different things like usefulness and efficiency, and they are judged as "bad" in relation to many different things, including the problems which they create.Metaphysician Undercover

    I would agree with that; except that utility is not the ONLY consideration. For pure mathematians, beauty and interestingness have higher virtue than utilility. Utility is for the physicists, and we know what THEY do with mathematics!! [They mangle the hell out if it for their own nefarious purposes].


    So a "good" tool might be very useful and efficient, but it might still be "bad" according to other concerns, accidental issues, or side effects.Metaphysician Undercover

    Yes, in general. But in this particular case, what you think is a defect is not. You're hung up on infinite decimals, but infinite decimals don't tell you anything about whether a number is rational or not. 1/2 = .5 = .49999.... It has TWO distinct decimal representions. That tells us nothing about the real number 1/2. It just tells us that decimal representation is a little buggy. Continued fractions are better. Turing machines are better. Infinite series representations are better.

    Bad is not necessarily the opposite of good, because these two may be determined according to different criteria.Metaphysician Undercover

    Yes all these generalities are wonderful but they're in service of a point that is wrong. Since is a finitary object, your general point doesn't apply here. There's nothing wrong with except your psychological block about it. Was a screechy math teacher mean to you? I can relate. I still can't do high school trig for shit because of my screechy trig teacher. She set my math development back years.

    Let's look at the Euclidian geometry now. In relation to the fact that this system produces distances which cannot be measured within the systemMetaphysician Undercover

    For Christ's sake, knock it off with this point. You're absolutely wrong.


    , can we say that it is bad, despite the fact that it is good in many ways?Metaphysician Undercover

    No.


    How should we proceed to rid ourselves of this badness?Metaphysician Undercover

    Who will rid me of this meddlesome priest!!

    Dude there is no badness. You had a bad high school math education -- not your fault, I'm sick at heart at the state of public math education -- but you refuse to move past it. You're just wrong on the facts.

    Should we produce another system, designed to measure these distances, which would necessarily be incompatible with the first system?Metaphysician Undercover

    Please stop. You were wrong the first time, you're wrong the hundredth time.


    Having two incompatible systems is another form of badness. Why not just redesign the first system to get rid of that initial badness, instead of creating another form of badness, and layering it on top of the initial badness, in an attempt to compensate for that badness? Two bads do not produce a good.Metaphysician Undercover

    You are so full of yourself you won't stop to engage with the points I (and others) have made to correct your misunderstandings. is a finitary object. It only requires a finite amount of information to completely specify its decimal digits. Why won't you acknowlege this fact?

    Come on, get real fishfry. Check Wikipedia on set theory, the first sentence states that it deals with collections of "objects".Metaphysician Undercover

    I am not responsible for what people type into Wikipedia. Some math articles are very good, some are highly misleading.

    In ZFC there is nothing called an object. There are only sets; and sets are an undefined term. ZFC consists of a collection of axioms about how an undefined operator called behaves. You can verify this by checking any university or graduate text on set theory.

    Once again you are giving the high school definition. It's confusing you.


    Then it goes on and on discussing how set theory deals with objects. Clearly set theory assumes the existence of objects, if it deals with collections of objects.Metaphysician Undercover

    Nonsense. Set theory precedes objects. We use set theory to construct numbers, functions, matrices, topological spaces, and all the other "objects" of mathematics. An object literally is some gadget we construct out of sets. And sets are undefined. Nobody knows what a set is. We have private intuitions, but set theory itself supports no preferred interpretation.

    I'm speaking sophisticated math to you and you just want to cling to what they told you in high school. That's your choice.

    This is why it is so frustrating having a conversation with you. You are inclined to deny the obvious, common knowledge, because that is what is required to support your position.Metaphysician Undercover

    I'm explaining to you what sets are, from the point of view of the mathematical discipline of set theory. You don't want to get it, fine by me. And you're right, we're pretty much at a point of completion here. I've made every point I have to make at least half a dozen times. I'm happy to abandon this thread.

    When I started, because of your arrogance and certainty and wordiness, I thought perhaps that I was missing some subtle philosophical viewpoint.

    Instead it turns out that you're just stuck on some psychological discomfort with what you learned (badly, and again not your fault) about the square root of 2 and its decimal representation.

    Having satisfied myself that I'm not missing some subtle point of philosophy; I have turned my efforts to trying to educate you about mathematics. You don't seem to be receptive and now I'm just annoying you. So I'll happily withdraw from the conversation. I stand by everything I've written.

    In the other thread, you consistently denied the difference between "equality" and "identity", day after day, week after week, despite me repeatedly explaining the difference to you.Metaphysician Undercover

    Incredible. I went to great lengths to explain to you that mathematical equality is an expression of the law of identity. That's what my Peano axiom proof that 2 + 2 = 4 was all about. You didn't even engage.

    Once again you have imputed to me a position that is the direct opposite of the one I expressed.


    You have not explained how acceptance of a mathematical tool, through convention, converts it from a funny gadget, to an object.Metaphysician Undercover

    I did. The passage of time. As the great physicist Max Planck said: science advances one funeral at a time. What he meant was that the old experts are not convinced by the new methods. Rather, the old guys die off and are replaced by a new generation that has grown up with the new ideas. That's how we came to accept rational numbers in the first place, and then irrationals.

    If you cannot demonstrate this conversion, then either the tool is always an object, or never an object.Metaphysician Undercover

    I already did, at least three times. Are you denying history? Read up on the history of negative numbers, zero, rational numbers, real numbers, complex numbers. I keep explaining this to you and you keep avoiding engaging with the point.


    Then an extremely bad tool is just as much an object as an extremely good tool, and acceptance through convention is irrelevant to the question of whether the mental tool is an object.Metaphysician Undercover

    You're so tied up in words you can't think straight.

    Until you recognize that an "element", or "member" of a set is an "object", you are simply in denial of the truth, denying fundamental brute facts because they are contrary to the position you are trying to justify.Metaphysician Undercover

    The truth is what you learned (badly) in high school or Wikipedia. Anything else is a lie. Whatever dude.

    The case I made is very clear, so let me restate it concisely. You appear to agree with me that mathematical tools are not objects, they are "mind" gadgets, yet you defend set theory which treats them as objects.Metaphysician Undercover

    There is no technical term called an object in set theory. It's something you made up. Sets don't contain "objects." They contain only other sets, if they contain anything at all.


    This is nonsense. I can very easily say "the highest number". Just because I say it doesn't mean that what I've said "completely characterizes" it. We can say all sorts of things, including contradiction. Saying something doesn't completely characterize it.Metaphysician Undercover

    You're embarrassing yourself. Your mathematical philosophy is unsophisticated because your knowledge of math is nil. You are psychologically stuck to your wrong ideas and you're incapable of engaging substantively with any point that anyone makes.


    if you switch to a different number system, one which is incompatible with the first from which the irrational number is derived, like switching from rational numbers to real numbers, this does not qualify as a resolution, if the two systems remain incompatible.Metaphysician Undercover

    Whateva whateva. I hope I'm getting to the end of this soon. This is my last post to you. I'm a fool if I continue to engage.

    For instance, if there is infinite rational numbers between any two rational numbers, and we take another number system which uses infinitesimals or some such thing to limit that infinity, we cannot claim to have resolved the problem. The problem remains as the inconsistency between "infinite" in the rational system, and "infinitesimal" in the proposed system.Metaphysician Undercover

    You are really good at writing stuff that sort of sounds intelligent, but doesn't hold up to scrutiny. That's why I was initially interested in your posts and why I took the trouble the read them. Now I've scrutinized them. You're ignorant about math and wrong on the philosphy.


    This has no relevant significance. To say "the square root of two", or "the ratio of the circumference of a circle to its diameter" is to give a 'finite description". We've already had the "finite description" for thousands of years. And, this finite description determines that the decimal digits will follow a specific order, just like your example of 1/3 determines .333.... The issue is that there is no number which corresponds to the finite description, as is implied by the infinite procedure required to determine that number.Metaphysician Undercover

    That doesn't even make any sense. It's a collection of words that seems to convey a coherent argument about something but simply doesn't.

    So now you don't believe in 1/3? I think you just refuted yourself.

    So my analogy of "the highest number" is very relevant indeed. Highest number is a "finite description". And, the specific order by which the digits will be "computed" is predetermined. However, there is no number which matches that description, "highest number", just like there is no number which matches the description of "the square root of two", or "the ratio of the circumference of a circle to its diameter", or even "one third".Metaphysician Undercover

    I'm out of steam.

    This demonstrates that there is a problem we have with dividing magnitudes, which has not yet been resolved.Metaphysician Undercover

    Dividing magnitudes. So now you don't believe in rational numbers either. We are making progress. That's right! Rational numbers are just as fictional or just as real as irrational numbers.

    Could understanding be dawning?


    Let me return your attention to this remark. If you agree with me, that the representations are "imperfect" from the start, then why not agree that we ought to revisit those representations. Constructing layer after layer of complex systems, with the goal of covering over those imperfections, doing something bad to cover up an existing bad, is not a solution.Metaphysician Undercover

    There's nothing bad to cover up. The bad thing is some misinformation you got stuck with in high school or earlier. You have to let go of things you think you learned that don't happen to be true.

    I learned a lot talking with you. Mostly I learned that I know a lot more about the philosophy of math than at least one person on this site who claims to know a lot about the philosophy of math. It's taken me years to get to this point. Thank you.

    Peace, friend.
  • Musings On Infinity
    My objection was only this one: BT doesn't make integration inconsistent.Mephist

    Oh I see. You were concerned that you'd change the value of an integral by moving things around. But right, that can't happen because the pieces aren't measurable so they can't be integrated anyway. Good point.

    You can reason about infinitesimal parts and be confident of the fact that integration works, if you decompose the object in open sets.Mephist

    Yes I see your concern now. Integration doesn't break and open sets are well-behaved. That's why B-T is a technical result that doesn't actually break anything important.
  • Musings On Infinity
    Yes of course they have to be isometries. I meant: there is no way of decomposing an object in an infinite set of open sets and then recomposing them in a different way so that each peace has the same measure but the sum of the measures of all the pieces is different. If this were possible, the theory of integration would be inconsistent.Mephist

    Yes, ok.

    I know your objection: if there is an infinite number of pieces the measure of each peace cannot be finite. OK, but you can build the limit of a sequence of decompositions, like you do with regular integration.Mephist

    I'm not objecting, I'm agreeing.

    I am not arguing that BT theorem is false, I am arguing that it works only because you perform the transformation on pieces that are not measurable.Mephist

    Yes of course! That's the point. Which reminds me of another reason the Vitali set is a warmup to B-T. The theorem only works because at least one of the pieces is nonmeasurable. If a set is measurable, an isometry must preserve its measure. If that's what you're saying, you're absolutely right.

    If the pieces were made using the decomposition in open sets, as with regular integration, it couldn't work. I know that you can even define a Lebesgue integral that is working on sets that are not open: this is not a necessary condition, but is a sufficient condition to preserve additivity.Mephist

    Sure. Agreed. All open sets are measurable. Can I prove that? In the reals it's easy because every open set is a finite or countable union of open intervals, intervals are measurable, and countable unions of measurable sets are measurable. In the plane or 3-space there's an analogous theorem but I'm not sure exactly what the wording is. Cartesian products of intervals are measurable so n-rectangles are, and you can probably express any open set as a countable union of rectangles but that's the part I'm fuzzy on. So I'm pretty sure all open sets in n-space are measurable but I'm only certain of the proof in one dimension.

    The axiom of choice lets Vitali cook up a nonmeasurable set, and that's what's happening here. The choice set on the orbits I believe isn't measurable, but don't quote me on that.
  • Musings On Infinity
    If topology has nothing to do with it why all the proofs of decomposition of objects that don't preserve volume are decomposing the objects in pieces that are not open sets?Mephist

    Question doesn't compute. IMO you are understanding some of the technical steps but not grokking the overall structure of the proof. I actually can't parse your question. Which proofs? What pieces? What not open sets? You're reading things into it that aren't there. I strongly urge you to examine the Wikipedia proof outline and put aside the paper you're reading because it's too detailed and doesn't show the big picture.

    Can you find an example of decomposing an object and then recomposing it with different volume where the pieces are open sets?Mephist

    Like f(x) = 2x stretching (0,1) to (0,2)? Yes. Open sets are easy if you don't require the maps to be isometries.

    You should start with the free group on two letters, that's the key to the whole thing. Forget continuity, nothing here is continuous. Rotations are continuous; but what's being decomposed paradoxically is the group of rotations. It's a little hard to get a grasp on this the first n times you go through it, for some large value of n.

    It's true that each individual rotation is continuous and carries open sets to open sets. But what's being decomposed is the collection of all the rotations; and this collection has a paradoxical decomposition by virtue of being a model of the free group on 2 letters. That is the one-sentence version of the proof.

    Start with the free group on 2 letters. Go through the Wikipedia proof. Abandon the difficult paper you chose to work with. My two cents.

    If topology has nothing to do with it why all the proofs of decomposition of objects that don't preserve volume are decomposing the objects in pieces that are not open sets?Mephist

    Because topology has nothing to do with it! The rotations are continuous but the group of rotations has a paradoxical decomposition. Any open interval is topologically equivalent to any other, regardless of length. Topology is too weak to preserve measure. We need isometries for that.

    In fact another one sentence summary of the proof is that while isometries preserve the measure of measurable sets; they do not necessarily preserve the measure of nonmeasurable sets.
  • Musings On Infinity
    Ok now that we have sort of a B-T discussion space, I want to suggest some warmup exercises to get a handle on the proof. I'll leave out all the details for brevity. These examples aren't actually part of the proof; but their methods give insight into what's going on when we translate the choice set on the orbits.

    * Consider the integers . Define two integers equivalent if their difference is a multiple of 5. This partitions the integers into five equivalence classes, each class countably infinite.

    Now consider each equivalence class. One is {-10, -5, 0, 5, ...}, another is {-9, -4, 1, 6, ...} and so forth.

    Now "using the axiom of choice," form a choice set consisting of one element from each equivalence class. Of course in this case we don't actually need choice, we could just take, say, the smallest positive element of each class. But we'll use the sledgehammer of choice just to get into the proper spirit.

    Such a choice set would look like, for example, {-10, 6, 12, 18, -1}. One element from each congruence class mod 5.

    Now we translate the choice set by every integer. {-10, 6, 12, 18, -1} + 0, {-10, 6, 12, 18, -1} +/-1, {-10, 6, 12, 18, -1} +/- 2, etc. In this way we recover all the integers.

    In fact every integer is the unique sum of one particular element of the choice set; plus one particular integer.

    What we've done is start by partitioning the integers into five classes, each countably infinite; and end up with a countable union of classes of size 5. We've "reversed the cardinalities."

    I have some pictures to go with this, is the exposition relatively comprehensible?

    * Ok next example, the Vitali set. We start with the real numbers and declare two reals equivalent if their difference is rational. I hope you see that while the formalities are clear, the intuition is hellacious. The equivalence classes are very hard to visualize. That's why this is such a cool example.

    Note that there are uncountably many equivalence classes; and each equivalence class is countable.

    We call the resulting set of equivalence classes . Now we do need the axiom of choice to form a choice set consisting of exactly one member of each equivalence class. Call the choice set in honor of Giuseppe Vitali, who cooked up this example in 1905.

    https://en.wikipedia.org/wiki/Vitali_set

    Ok now we do the same trick. Using the fact that is an Abelian group under addition, we can show that by translating by each rational number in turn, we recover the entire set of reals.

    Again, each real number is now expressed uniquely as the sum of a particular element of and some rational.

    But now what we've done is partition the reals into an uncountable union of countable sets; and by translating the choice set, we ended up with a countable union of uncountable sets! Again we've reversed the cardinalities.

    Why does this matter? In Vitali's example he restricted the operations to the unit interval, with the operation of "addition mod 1", or circular addition of reals. So 3/4 + 1/2 = 1/4, you wrap around. And now, when we have the unit interval expressed as a countable union of translations of , we can apply countable additivity to show that the measure of can not possibly be defined. If the measure of is zero, by countable additivity the measure of the unit interval must be zero. If it's positive, the measure of the unit interval is infinite.

    So there is no translation-invariant, countably additive measure on the real numbers that assigns 1 to the unit interval. is in fact a non-measurable set: a set of real numbers that can not possibly be assigned a size or a probability in any sensible way.

    https://en.wikipedia.org/wiki/Non-measurable_set

    * With these two examples in mind, we see how we partition a set into equivalence classes; take a choice set; then translate the choice set to either reverse cardinalities or get some other nice property that we care about.

    So in Banach-Tarski, we start with the set of rotations generated by our two magic matrices. We take a choice set on the collection of partitions. Now we do NOT have a nice Abelian group; but we can use the properties of group actions to show that each element of the original set is expressed uniquely as a rotation applied to some element of the choice set. So we have the unit sphere expressed as a union of rotations in applied to the choice set. And since is a copy of the free group on two letters, the paradoxical decomposition of induces a paradoxical decomposition of the sphere.

    I hope this makes some sense. I find that it helps me to understand the structure of the final step of the proof.
  • Musings On Infinity
    [Revivifying this thread to comment on Banach-Tarski]

    I linked it in the post just before this one. Here's the link:
    https://thephilosophyforum.com/discussion/comment/302364
    Mephist

    Ok. I didn't go through it in detail. You shouldn't get hung up on the particular rotations, that's not relevant. What's important is that the isometry group of 3-space contains a copy of the free group on two letters, which already has a paradoxical composition.

    I haven't time tonight (and I'm kind of busy for a few days and probably haven't the concentration anyway to go through your post line by line) but I recommend the Wiki outline of the proof, which I find pretty clear. https://en.wikipedia.org/wiki/Banach%E2%80%93Tarski_paradox

    But you're asking for things to be continuous or preserve topologies or whatever, and those things have nothing at all to do with the proof. As I say I don't have the time/energy right now to go through your post but you're missing some of the overall structure. All of the transformations generated by the two matrices are isometries, or distance-preserving transformations. They're all rotations around the origin in fact. And the group of isometries contains a copy of the paradoxical free group. That's the main idea to absorb about the proof.

    See https://en.wikipedia.org/wiki/Paradoxical_set

    https://en.wikipedia.org/wiki/Free_group

    I'll look at your proof some more but actually from what you wrote you're probably working from a source that emphasizes the particular matrices, but that's a troublesome way to go. All that's important is that there exist a pair of rotations that are independent, in the sense that no finite combination of the rotations and their inverses can ever be the identity rotation. That's why they are an example of the free group on 2 letters.

    Def see this page.

    https://en.wikipedia.org/wiki/Banach%E2%80%93Tarski_paradox

    ps -- I glanced at your link. That paper's way too detailed and technical. Use the Wiki outline. There are four steps:

    * Grok the sublime beauty of the paradoxical decomposition of the free group on 2 letters, . In the proof sketch you gave, you did this part in the context of the two rotation matrices and that's terribly confusing. You can see from the free group that the paradox is already inherent in simply composing any two invertible operations. It's better to see this part first, before diving into the rotations.

    * Take on faith that there are a pair of rotations of the unit sphere that are independent, hence are a model of . We don't care what the two rotations are. This is a technical part of the proof that's perfectly ok to simply accept.

    * Let H be the copy of generated by the two rotations of the unit sphere. Let H act on the sphere. The action partitions the sphere into disjoint orbits. You are correct that each orbit is countable and that there are uncountably many of them. So you're getting most of this right.

    * Pick a choice set consisting of one element from each orbit. We recover the sphere by translating the choice set; analogous to the way we recover the reals by translating the Vitali set. If you have not studied the example of the Vitali set, start here. It's not directly relevant to Banach-Tarski but it's same process of taking an equivalence relation and translating back a choice set on the equivalence classes to recover the original set. This is how to think about B-T.


    https://en.wikipedia.org/wiki/Vitali_set


    * Finally you apply the original paradoxical decomposition of the free group. I think I'm a little fuzzy on this point tonight but I believe I understood it at one point a few months ago. That was five steps. Wiki has it as four.

    ps -- Ah I think I remember. After translating the choice set, every point on the sphere can be uniquely expressed as some particular rotation applied to some particular point in the choice set. Now when you apply the paradoxical decomposition of the free group to the set of rotations, you get a paradoxical decomposition of the sphere, modulo some details.

    If you're having intuitions of topologies or continuity, those are the wrong intuitions to be having. What's interesting though is that each orbit is dense -- that is, arbitrarily close -- to every point on the sphere. That's why I said earlier that the orbits are disjoint but in no way separated. They're like the rationals in the reals. Arbitrarily close to every real, but you couldn't cleanly separate them out.

    I hope some of this helps. I'm not an expert. I can see that some of my exposition is fuzzy. I've been at this proof for quite some time. A few months ago I started writing up a simplified explanation and at one point convinced myself I understood about 95% of everything that was going on. Tonight I've got maybe 50 or 70%. But perhaps some of what I wrote will connect with your intuition. But forget continuity. The "pieces" of the decomposition are wildly discontinuous.

    Have you seen the Vitali set? You should start there. Define an equivalence, take a choice set, translate the choice set back to recover the original set.
  • My own (personal) beef with the real numbers
    I linked it in the post just before this one. Here's the link:
    https://thephilosophyforum.com/discussion/comment/302364
    Mephist

    I made some comments in the other thread so as not to pollute this one.

    https://thephilosophyforum.com/discussion/comment/368991
  • What is the difference between actual infinity and potential infinity?
    I submit that 5 is prime and the square root of 2 both exists and is rational. . . . But they are true.
    — fishfry

    What am I missing here?
    jgill

    I'm making the point that the facts of math are not quite as arbitrary as the facts of other formal games such as chess. That's something peculiar or interesting about math. We can't make up a form of math where 5 isn't a prime (in the usual integers). Yet 5 and "prime" are abstract and somewhat fictional entities.

    I'm not entirely sure what your question was. But the point is that math isn't like driving laws or chess. Some things in math are objectively true yet not facts about the physical universe.
  • My own (personal) beef with the real numbers
    I am satisfied with this principle if we can apply it consistently. We do not measure mathematical "objects", they are tools by which we measure objects. That's why I argued that they are not proper "objects".Metaphysician Undercover

    Ok. First, if you have been talking about mathematical objects and not physical space, my misunderstanding. But then all your mathematical objections will collapse.

    Secondly, a terminological quibble. In math there is a thing called a measure. It's a generalization of the idea that the unit interval has length 1, and a rectangle of sides 2 and 3 has area 6, and so forth. So it's a little better not to use that word.

    If you're talking about distances, better to use the word metric. A metric is a distance function. For example in the Euclidean plane, the metric, or distance function, is given by the usual Pythagorean formula of the square root of the sum of the differences of the respective squares of the coordinates. That is, if and are points in the plane, their distance from one another is

    . In n dimensions the formula is analogous. But there are also weirder metrics. A metric is the general name for any distance function.

    Now back to your quote. Of course we measure mathemtical objects. A unit square has side 1, area 1, and its diagonal ... well you know what its diagonal is. In fact it falls out of the Euclidean distance formula as the distance between the origin and .

    Now let's apply this to set theory. Cardinality, for example is a measure.Metaphysician Undercover

    Cardinality is not a measure in the technical sense. It's a way of assigning a size to a set. I don't think there's a name for it.

    If the applicable principle is that we do not measure mathematical "objects", then why allow this in set theory? It's inconsistency.Metaphysician Undercover

    Of course we can assign a length or area or volume to mathematical objects. The unit interval has length 1, the unit square ... oh we've been over this already.

    So either we can measure mathematical objects, like squares, and the sides of squares, just like we can measure the cardinality of sets, or we cannot measure these so-called mathematical objects.Metaphysician Undercover

    Of course we can measure, or assign a length/volume/area to, or find the distance between pairs of, mathematical objects.

    If I earlier thought you were objecting to physical measurement, my misunderstanding.

    But of course we can measure or assign size to mathematical objects in many different ways, depending on context.


    I'm fine with the latter principle so long as we maintain consistency.[/quote]

    We do. The rules are laid out in the articles on measure theory and metric spaces that I linked.


    But if we allow that we can measure these so-called objects, then we can measure a square, and find that the diagonal cannot be measured.Metaphysician Undercover

    You are painfully misinformed about this. The square of the diagonal of a unit square is . It's a perfectly good real number; and metrics, or distance functions, are defined as functions between pairs of objects and the nonnegative real numbers (satisfying some distance-like properties).

    It's what we call an "irrational number", implying an immeasurable length. Are you familiar with basic geometry?Metaphysician Undercover

    You keep saying an irrational number is "immeasurable" but that's simply false. You're just wrong about that. You're still humg up on decimal representations but I'll show you soon that you're wrong about this.


    This is not at all what I've been saying, so I think we might not really be making any progress.Metaphysician Undercover

    No we're good, I thought you were saying physical distances can't be measured. But if you're talking about mathematical objects, my misunderstanding. And now that I understand what you're talking about, you're just wrong. We can use metric spaces or measure theory to measure distances and generalized volumes (length, area, volume, etc.)


    Neither you nor I is talking about physical objects here. What we are talking about is the "made-up gadgets" which you describe here.Metaphysician Undercover

    Understood.

    You seem to imply that there is a difference between these funny gadgets, and "first-rate mathematical objects"Metaphysician Undercover

    No, I'm pointing out that there only seems to be a difference depending on what age one lives in. If you live in the age of integers you don't believe in rationals. You're stuck in the age of rationals and don't believe in irrationals. Matter of history and psychology.

    I deny such a difference, claiming all mathematics consists of made-up gadgets, and there is no such thing as mathematical objects.Metaphysician Undercover

    We're in agreement then. But that's what a mathematical object is. A made-up gadget that, by virtue of repetition, gains mindshare.



    But this is contrary to set theory which is based in the assumption of mathematical objects.Metaphysician Undercover

    I've studied set theory and read a number of set theory texts. I've never read or heard of any such thing. Set theory in fact is the study of whatever obeys the axioms for sets. If you ask a set theorist what a set is, they'll say they have no idea; only that it's something that obeys whatever axiom system you're studying.

    You're making stuff up to fill in gaps in your mathematical knowledge. Set theory doesn't assume anything at all. It doesn't assume it's "about" anything other than sets; which are things that obey some collections of set-theoretic axioms.


    If you really think that a "funny gadget" becomes a "mathematical object" through use, you'd have to demonstrate this process to me, to convince me that this is true.Metaphysician Undercover

    But I already did. From the naturals to the integers to the rationals to the reals to the complex numbers to the quaternions and beyond. At each stage people didn't believe in the new kinds of number and though it was only a kind of "calculating device." Then over time the funny numbers became accepted. This is a very well known aspect of math history.

    How can you not see that this is a problem for set theory?Metaphysician Undercover

    Because I'm not making up wild stories about set theory as you are.

    Set theory assumes that it is dealing with real, actual mathematical "objects".Metaphysician Undercover

    Not at all. I know that in high school they tell you that a "set is a collection of objects." Nothing could be further than the actual truth. Sets as mathematicians understand them are very strange. They're simply abstract thingies that satisfy some axioms that we write down.


    That is a fundamental premise.Metaphysician Undercover

    It's something you made up. Or maybe someone told you that. They were wrong. Set theory doesn't assume any objects at all. In fact ZFC is a "pure" set theory, meaning that the only things that can be elements of sets are other sets. There are no other types of objects at all! Only sets, and we don't even know what those are!

    For the record there are also set theories with urelements, meaning things that can be members of sets that are not themselves sets.


    Now you agree with me, that mathematics can never give us this, real or actual things being represented by the symbols.Metaphysician Undercover

    What do you mean by real or actual things? In the physical world? Well, physicists use math to model electrons and gravity and quarks and stuff. Maybe you should ask a physicist.

    But do you mean how can sets be used to model mathematical objects like numbers, functions, matrices, topological spaces, and the like? Easy. We can model the natural numbers in set theory via the axiom of infinity. Then we make the integers out of the natural, the rationals out of pairs of integers, the reals out of Cauchy sequences of reals, the complex numbers out of pairs of reals, and so forth. If you grant me the empty set and the rules of ZF I can build up the whole thing one step at a time.


    So why don't you see that set theory is completely misguided?Metaphysician Undercover

    You haven't made any such case. On the contrary, your questions all have straightforward answers.

    So your argument is that the "funny gadget" gets made into a "first-rate mathematical object" through convention, just like driving laws.Metaphysician Undercover

    No, I took pains to make a distinction. Driving laws are completely arbitrary. But many mathematical ideas are forced on us somehow, such as the fact that 5 is prime.


    But those are ";laws", not "objects". Let's suppose that the mathematical symbols referred to conventional laws instead of "objects", as this is what is implied by your statement. How would this affect set theory? Remember what I argued earlier in the thread, sometimes when a symbol like "2" or "3" is used, a different law is referred to, depending on the context.Metaphysician Undercover

    Yes, I thought at that time that either yu were making a point of great subtlety, or else that you were insane. By reading your posts I have determined the latter. I don't mean to be pejorative here. But you said at one point that when we say "4 + 4 = 8", the two instances of the symbol '4' mean or refer to different things. That's ... Look man that's just bullshit. I can't be polite about this. That's a very bizarre idea.

    I don't see how "the square root of 2 exists" could possibly be true, It is an irrational ratio which has never been resolved, just like pi.Metaphysician Undercover

    You're still hung up on decimal representations; which I've said (several times now) are NOT determinative of whether a given real number has infinitary nature.

    Here's an example. Take 1/3 = .333333.... Would you say that 1/3 is not resolved or requires an infinite amount of information? But it doesn't. I could just as easily say, "A decimal point followed by all 3's." That completely characterizes the decimal representation of 1/3. I don't have to physically be able to carry out the entire computation. It's sufficient that I can produce, via an algorithm, as many decimal digits as you challenge me to.

    Likewise there is a finite computer program that completely characterizes . I don't have to write out all the digits. I only have to write down a FINITE description of an algorithm that produces as many digits as you like. This is easily done.



    How can you assert that the solution to a problem which has not yet been resolved, "exists"?Metaphysician Undercover

    It has been completely resolved. You can't write down infinitely many digits any more than you can write down all the digits of .333... But in the case of 1/3, there's a finite-length description that tells you how to get as many digits as you want. And with square root of 2, there is ALSO such a finite-length description. Would you like me to post one?

    Isn't this just like saying that the highest number exists?Metaphysician Undercover

    No.

    But we know that there is not a highest number, we define "number" that way.Metaphysician Undercover

    Bad analogy, nothing to do with the fact that computable numbers like 1/3, , and only require a finite amount of information to completely determine their decimal expressions.

    Likewise, we know that pi, and the square root of two, will never be resolved,Metaphysician Undercover

    I showed how to characterize pi a few days ago as the Leibniz formula. The square root of 2 has a very easy program to calculate its digits.

    I really hope you'll consider the example of 1/3 and the fact that we can predict or determine every single one of its decimal digits with a FINITE description, even though there are infinitely many digits. Square root of 2 and pi are exactly the same. They are computable real numbers. There is a finite-length Turing machine that cranks out their digits.

    Here's a Python program that prints as many digits of as you like. It uses a simple high/low approximation method. We know because . So we split the difference and guess 1.5. But 1.5 squared is 2.25, a little too big. So we split the difference between 1 and 1.25 and try that. The longer we run the algorithm the more digits we get. Just like the longer we write down 3's, the more decimal digits of 1/3 we get.


    #!/usr/bin/python3
    
    low  = 1
    high = 2
    
    loops = 1000
    
    for i in range(loops) :
        lowsq  = low * low
        highsq = high * high
    
        trial   = (low + high) / 2
        trialsq = trial * trial
    
        if trialsq < 2 :  # too small
            low = trial
    
        else :   # too big. 
            high = trial
        
    print(trial)    
    

    This simple little FINITE STRING OF SYMBOLS cranks out successively better and better approximations to the more iterations you do. Of course we can't physically write down all the digits because physical computations are resource-limited. But in principle we can; just as "keep writing threes" is a recipe for the decimal representation of 1/3.
  • Most Important Problem Facing Humanity
    Climate denierXtrix

    The funny thing is I never said that. What triggered you? Was it the mastodons? PETA member?
  • Most Important Problem Facing Humanity
    I would like to get a sense of what most people on here believe is the most important problem facing humanity today.Xtrix

    You know it's funny. I quoted the exact words you used to start this thread. Taking you at your word, I gave you my opinion.

    Now you might have said, "Well that's not what I was expecting but thanks for contributing your opinion."

    Instead, you seem emotionally triggered by the fact that I dared to express an opinion you don't hold. And not that unusual of an opinion. Read your Chomsky. "Manufacturing consent." Read McLuhan on media. He predicted all of this decades ago. Much of what you think and believe is a function of what you read in the media. Check who owns the media. Do I really need to explain this stuff to people? You think the media are selfless public servants and nobody has an agenda?

    And did I really say I don't believe in ... well whatever cause is near and dear to your heart? No. I only pointed out that most people in the developed West have no idea what a problem is. Don't know if you've noticed, but there's a worldwide revolt against the elite who think they know better but actually don't know anything at all.

    The main thing is that you said you wanted opinions; but when presented with one, you retreated into anger and derision. I think you must be what they call a snowflake. Terrified of hearing an opinion you don't like.
  • Most Important Problem Facing Humanity
    Please substantially tell us and the science community how climate change is “hysteria.”Xtrix

    Greta. I rest my case.

    [Oh boy now I've done it.]
  • Most Important Problem Facing Humanity
    What a stupid, stupid position.Xtrix

    Always glad to see substantive argument on the Philosophy Forum. Socrates watches with admiration and approval from his place in the pantheon of philosophy, "the study of the fundamental nature of knowledge, reality, and existence." You know so much, and the rest of us so little.

    You need to get your head out of your daily diet of media hysteria.
  • Most Important Problem Facing Humanity
    I'll toss in my two cents that this is a beautiful list of first world problems. Back in the day, and in many places in the world today, finding food and water to get through the next 24 hours was and is the most pressing problem. That it never crossed your mind is a sign of just how far we've come and how privileged in time and space we are. 790 million people currently don't have access to running water. THAT"s a problem, my friend. A problem that you don't have. Count your blessings.

    I also want to note to the overpopulation crowd that the actual biggest populate-related problem is UNDER-population. The Western world is not reproducing at a replacement rate and hasn't been for decades. There won't be enough workers to support the ever-aging population.

    This isn't the place for this discussion, but if you Google around you'll easily find many articles explaining this point of view. That there aren't enough people being born to sustain our way of life. It's underpopulation and NOT overpopulation that's the problem.

    But like I say, when we lived in caves we didn't worry about how many cave people there would be in fifty years. We were just hoping a nice meaty mastodon would wander by so we could spear it for dinner. Ogg a few caves down has this "fire" stuff so we don't have to eat raw mastodon meat anymore. I'm sick of raw mastodon meat.

    Now THOSE are problems. Worrying about crap you read in the mainstream media is a fool's game. I suggest that in the new year we all try to focus on what's real and what's merely illusion.
  • What is the difference between actual infinity and potential infinity?
    Thank you fishfry. I'm vey impressed that you actually took the time to read and try to understand what I was saying.Metaphysician Undercover

    You're welcome.

    Most just dismiss me as incomprehensible or unreasonable ...Metaphysician Undercover

    No, really?

    Just kidding!! I enjoy the new civility and hope to perpetuate it.

    I couldn't tell who was crazy, you or me. You were so sure of yourself when you said I didn't understand anything about anything. I wanted to find out what was going on. I believe I did. You think math should be physics. You think perfectly accurate distances exist in the real world. You seem to deny abstraction, as in your claim that squares are "impossible," your word. You did not yet take my point that rational numbers are just as questionable as irrationals. I mean, what the hell is , anyway? You can't measure it. You can't show it to me. You can't evenly divide a pie into seven pieces. [Insert clever pun on pi here]. So in fact your psychological belief that rational numbers are more deserving of mathematical existence as irrational ones, is simply that: a psychological belief.

    I have explained in recent posts (here and the other thread) that:

    * The number is a made-up mathematical gadget that allows us to solve the equation .

    * is a made-up mathematical gadget that allows us to solve the equation .

    * The number is a made-up mathematical gadget that allows us to solve the equation .

    * The imaginary unit is a made-up mathematical gadget that allows us to solve the equation .

    In each case, mathematicians of a given historical age become interested in an equation they can't solve. They say, "Well what if there were a funny gadget that solved the equation?" Then after a few decades the made-up gadget becomes commonplace and people come to believe in it as a first-rate mathematical object, and not just a convenient fiction. Eventually we can construct these gadgets both axiomatically in terms of their desired properties; and as explicit set-theoretic constructions. They do indeed become real. Mathematically real, of course. Nobody ever claims any of this stuff is physical. You are fighting a strawman.

    Note also that new classes of numbers can be explained as algebraic phenomena, not just geometric ones. The diagonal of a square is one vision; the solution to an equation is another. The fact that we have multiple ways to arrive at the same place is a clue that we are dealing with truth. Not physical truth. Abstract mathematical truth. If the geometers hadn't discovered the square root of 2, the algebraists would have.

    So this is where I want to engage. You seem to want math to be what it can never be. You want an abstract, symbolic system to be real, or actual. That can never be. Your hope can never be realized.

    As far as the larger philosophical issue:

    We agree math isn't literally true about the world. We wonder what its status is. Well, there are things that are physical and things that are abstract. Physical things are presumed true. That's a rock on the ground, if I pick it up and drop it, it accelerates toward the earth at 32 feet per second.

    But abstractions can be real as well. Driving on the left or right is a social convention that varies by country. It's artificial. Made up. It's nothing but a shared agreement. It could easily be different. Yet it can be fatal to violate it. Driving laws are social conventions made real. See Searle, The Construction of Social Reality.

    I submit that 5 is prime and the square root of 2 both exists and is irrational. Those are abstract truths. They are not physical. But they are true. [Typo fixed].

    We can go further. "5 is prime" is not like traffic lights. In chess we can make up variants of the game where the pieces are arranged differently or there are pieces with different types of moves. Math is a formal game as well, but we are NOT FREE to say that 5 is not prime. This I think is the core mystery of math. 5 is prime even though there is no 5 and there are no primes.
  • What is the difference between actual infinity and potential infinity?
    It seems to me your entire post is deeply confused, rampant with ambiguity, amphiboly, conflation, undefined terms - or if they'e defined then the definitions are not held to - and faulty argument, all in a toxic mix and mess, that like most messes, is easy to make but labor intensive to clean up .tim wood

    Thanks man. I was going to say the same but @Metaphysician Undercover and I have reached a point of mutual civility and I'm trying to keep that going. So I didn't say what you just did, though I endorse and agree with it.

    I have been reading @Meta's post and it's hard to know where to start. @Meta, do you agree that math isn't physics? You complain that we can't measure but we can't measure 1 either. All physical measurement is approximate and never exact. You don't seem to appreciate this point.

    When you say "squares are impossible" you seem to be denying abstraction. Of course there are no perfect right angles in the world, but there are in abstract reasoning. You can't deny abstractions, civilization runs on them.

    I'm afraid you have your own free will and I can't make you go away.Metaphysician Undercover

    Hey it's great. @Meta is polite to me now and insulting others. Thanks @Tim for bearing this burden on my behalf.
  • My own (personal) beef with the real numbers
    I would say that it works even if you consider infinitesimals as really existing entitiesMephist

    LOL Now you're trolling me seeing if I'll take the bait. There are no infinitesimals in the real numbers. If you're working in some other number system please say that. As I said earlier I have no problem with people informally thinking in terms of infinitesimals; but I do object to muddying the official formalism.


    As I wrote in my explanation about Banach-Tarski mounts ago, the theorem works because it uses isometric transformations, but applied to set of points that are isolated from each other (not on open sets). If you impose the restriction that your isometric transformations should be even continuous (going from open sets to open sets), you can't do it any more.Mephist

    I'm not sure what you mean. Can you please link your earlier post on B-T? The point sets in B-T are not isolated from each other, in fact the orbits are dense. They're disjoint from one another but not isolated. We should have a nice Banach-Tarski thread sometime, the subject keeps coming up.
  • Universe as simulation and how to simulate qualia
    Again, I am not promoting any philosophical view, just trying to make very general but meaningful statements that I think everyone can agree on, so we can talk about the same thing rather than talking past each other.Zelebg

    Well I can't agree till I understand what you're saying. Why can't a computer, or an "information processing system," be conscious? We're information processing systems and we're conscious.
  • Universe as simulation and how to simulate qualia
    What if I told you that feelings are a special kind of information or signal that carries its meaning within? Like a magical language no one has to learn, but is innately and universally “understood” by all the living.Zelebg

    Just jumping in to the thread, curious about this. Why the living? If consciousness (feelings, qualia, etc.) are information, then we already know that the substrate doesn't matter. There's a Youtube video of a logic gate made from dominos. That's in fact the argument of those who say we could "upload" our minds to computers, or that we ourselves are computers.

    But you're saying that only the living get the privilege of experiencing experience. If I take the same program and put it in a computer, it executes but doesn't feel anything. But if I run it on a living thing with a sufficiently complex nervous system, then consciousness happens.

    Is that a fair summary of your point of view? Do people think life is necessary for consciousness, or not? Must robots be condemned to be philosophical zombies? Or might my Roomba be ruminating?
  • My own (personal) beef with the real numbers
    It doesn't work because in integral calculus you have to take "open sets" as infinitesimal pieces ( but I would prefer to not go into details about this issue, because surely fishfry will read this and will not agree :wink: )Mephist

    Oh gosh. Thanks for mentioning it.

    I was idly skimming through the many posts in this thread that I hadn't read. And I swear this is how my brain works. I zeroed in on this particular comment like a laser. That's not an especially good quality because I often miss the larger points people are making. I'm an excellent proofreader too. Grammar and spelling errors literally jump right off the page as I read. Terrible affliction in a day and age when nobody gives a shit about spelling or grammar. Spelling and grammar are tools of patriarchical and colonial oppressors. Such is the zeitgeist.

    You mentioned integrals. A lot of people think of an integral as the sum of the areas of infinitely many infinitely thin rectangles. I have no problem with that. That's how everyone thinks about them and that's perfectly fine. Professional physicists do in fact think exactly this way all the way up to the highest levels. It doesn't matter.

    I have no beef with how anyone thinks about math or visualizes it or simplifies it in their minds.

    But you did give a wrong and misleading definition of an open set. I do have to say that. Open sets are really important. An open set in the reals is just like an interval without its endpoints. What matters about it is that "all its points are interior points." It doesn't include any points of its boundary. That's what makes open sets have the interesting properties that they do.

    They're not really infinitesimal. They can be arbitrarily small. But they aren't "infinitely" small. In fact that is the great "arithmetization of analysis," the great founding of the continuous world of calculus on the discrete world of set theory. Instead of saying things are infinitely small, from now on say they're arbitrarily small. For every epsilon you can go even smaller. But in any individual instance, still nonzero. That's the essence of open sets.

    Ok I quibbled again. I had a great course in Real Analysis with a gifted professor. Open sets are very near and dear to my heart. But if you substitute "infinitely small" with "arbitrarily small," each time you do there will be that much more clarity and correctness in the universe. We can literally reverse entropy by fixing typos. Think about that.
  • My own (personal) beef with the real numbers
    OK, then there is this little "glitch" in the fabric of the universe named Banach Tarski theorem... :smile:Mephist

    Banach-Tarski means nothing about actual space. It's a valid technical result that applies to mathematical Euclidean space. There's no reason to believe that the universe behaves exactly the way Euclidean space does. This seems to be a common theme here lately, but I think it's mostly a strawman argument. I don't think there's anyone seriously suggesting that the actual universe is exactly like the mathematical real numbers. I for one don't believe that in the slightest. I think mostly that the people who think that haven't given the matter much thought; and once you start thinking about it, it becomes perfectly clear that the real numbers are a mathematical model that works amazingly well, in spite of the fact that it's so unlikely to be anywhere near close to the "truth," if there even is any such thing as a truth of the matter. Most likely it's turtles all the way down.

    There aren't any analogs of mathematical "points" in the real world, little zero-dimensional zero-sized thingies that somehow occupy a "location" in space. I don't believe that for a moment. I really don't think anyone else who's thought about the matter seriously does either. That's my opinion anyway. I like math but I never confuse it for reality. I think a lot of people in online forums are angry at math for making the claim of being a perfect representation of the universe; but math does not make that claim. Math asks to be taken on its own terms.

    Banach-Tarski is a valid theorem. I heard that John von Neumann was the one who first noticed it in the 1920's. They were looking at how group theory interacts with geometry and measure theory, and this little paradox shows up. Mathematicians tend to delight in such results. They don't throw up their hands and go, "Oh woe is us, the physicists will make fun of us. Or even worse, the philosophers will!" They don't think that way. A cool result is a cool result. As Russell noted, math is about investigating the logical consequences of various sets of premises. It's not necessarily true or meaningful. Sometimes it is. Depends on what you use it for.

    I'm with Hardy, who held that the the more useless a branch of math, the more beautiful it was. He applied this to his beloved number theory, which for over 2000 was regarded as a supremely beautiful and supremely useless part of math. How would Hardy feel if he came back and found out that in our very lifetimes, starting in the 1980's, number theory became the basis of Internet security, and is now the most applied branch of math you can imagine! I hope he'd have a sense of humor about it; and also a sense of wonder at how purely abstract math, considered useless for millennia, one day becomes the very heart of world commerce.

    Hardy was the guy played by Jeremy Irons in The Man Who Knew Infinity, which if you haven't seen it, please do immediately. Besides being a mostly true account (for a Hollywood movie) of the miraculous and tragically short life of Ramanujan; it's also a meditation on the relation of intuition to formalism in math. Visions from the Goddess versus formal proof.
  • Mathematicist Genesis
    I'm not sure why NOR is important to you
    — fishfry

    Because it's a sole sufficient operator.
    Pfhorrest

    I remember my logic professor telling us about the Scheffer stroke, which can be used to define all the other logical operations. It's equivalent to NAND. So NAND is as good as NOR for your purposes. But isn't it mostly a curiosity? We can define all the other logical relations in terms of a single one. Ok. But why make it a focus of interest?
  • Why do you think the USA is going into war with Iran?
    Furthermore, I seriously suspect that Trump was informed about the operation only after the facts. This is quite a victory for "incorruptible" Benjamin, of course. He must have had a big late-night party with his friends in Tel Aviv after this.alcontali

    Sadly I must agree with you. Trump's been captured by the neocon warmongers. He got rid of Bolton but Bolton is still running US foreign policy. Trump's a fool to get sucked into this. Some Iraqis attacked the Green Zone? Why do we have a fortress embassy in Iraq in the first place? We should have left years ago. We never should have gone in. I'm in total despair about what passes for US foreign policy.

    If Trump gets involved in a shooting war w/Iran he won't be reelected. His supporters believed him when he said he'd get us out of the stupid Middle East wars, not get us into more of them. And Iran's no military pushover like Iraq was. I'm hoping for the best here, that's all anyone can do.
  • Why do you think the USA is going into war with Iran?
    There's no war, everyone needs to chill out. As Trump said, he killed the Iranian general to avoid a war, not to start one. Trump is the only person in Washington trying to not have a war. That's the platform he was elected on. I believe if he got us into another major Middle East war, that's the one thing that would cost him the presidency. I think he knows that too.
  • Mathematicist Genesis
    ↪fishfry I think you meant to quote the part where I wrote "And the complement of the empty set, all that is not nothing, is everything. The end." That part was a joke, and I immediately backtracked to get back to the actual point of that first post.Pfhorrest

    I think I realized that a little later but didn't go back and update my post.

    I could use a little clarification though, because as I understand it the logical operations are all equivalent to set operations, and as I understand it complement is the set-theoretic equivalent of negation, but negation isn't quite the same as joint negation though it can trivially be made to function as such (just feed an operand into both arguments of NOR instead of the single argument of NOT), so I'm not entirely sure if complement can be treated as the set-theoretic equivalent of joint negation too, or just plain unary negation, and in the latter case, what actually is the set-theoretic equivalent of joint negation?Pfhorrest

    Ok so there is no complement of the empty set, but the negation of T is F and vice versa, is that what you mean? I think you want negation in a Boolean algebra, not in set theory at large, if you're trying to formalize negation. I'm not sure why NOR is important to you, it's somewhat obscure in logic although I believe it's more important in computer chip design. Or actually I'm probably thinking of NAND gates.

    LOL I just checked it out on Wiki and it says, "The NOR operator is also known as Peirce's arrow ..."

    That Peirce really gets around!

    https://en.wikipedia.org/wiki/Logical_NOR
  • How big will the blood bath be when the economy flips?
    ↪fishfry what sites do people discuss 2nd amendment without behaving like they could kill someone any day? I have done some work on the topic and I cant find any serious, or more notably, kind, people to look at it.ernestm

    Gun rights aren't a core issue for me. I don't actually know any gun rights sites or spend any time thinking about the issue. I do read some right wing, nativist and libertarian sites where people strenuously argue for gun rights. They all tend to be the responsible gun owner types generally making abstract points about freedom and law, not people hoping for mayhem. Note, I read the left wing wackos too. I've always had the ability to read things without necessarily agreeing with them. I regard myself as a centrist wacko.
  • What is the difference between actual infinity and potential infinity?
    Part 2


    I will remind you, that Pythagoras demonstrated the irrational nature of the square. The relation between two perpendicular sides of a square produces the infinite, which as I argued above is bad. This makes the square a truly impossible, or irrational figure. And, all "powers" are fundamentally derived from the square. Therefore any exponentiation is fundamentally unsound in relation to a spatial representation..Metaphysician Undercover

    A lot here to work with. Let me break it down a little at a time. I've already made many of these points in other threads lately so I'll try to keep this short.


    I will remind you, that Pythagoras demonstrated the irrational nature of the square.Metaphysician Undercover

    Yes. This is true. Euclid's version of the proof, from around 300BC, shows that there are no two integers whose ratio squared is 2.

    It shows that the square of the ratio of two integers is never 2. This is a result in number theory. It's indisputable.

    That it comes up so naturally, as the diagonal of a unit square, shows that (at least some) irrational numbers are inevitable. Even if we're not Platonists we suspect that a Martian mathematician would discover the irrationality of . There's a certain universality to math. Euclid's proof is as compelling today as it was millenia ago. The philosopher has to acknowledge and account for the beauty, simplicity, and power of Euclid's proof, undiminished for 2400 years; not just deny mathematics because some number doesn't happen to be rational.



    The relation between two perpendicular sides of a square produces the infinite ...Metaphysician Undercover

    No. No no no no no no and no. I've hit this point several times in other recent threads, and already enumerated these bullet points over in the other thread. Let me just recapitulate these points briefly.

    * A real number is not its decimal representation. happens to have an infinite, nonrepeating decimal representation. That's an artifact of decimal notation, not a characteristic of the real number itself. There are many finite characterizations of .

    * is a computable real number in the sense of Turing 1936. Therefore even a diehard constructive mathematician would gladly accept the existence of . From now on when I say existence I mean mathematical existence. I'll stipulate that we can't measure in the real world. As long as you'll stipulate that we can't measure 1 either. So the real world doesn't even come into play here. Measurement's approximate. Mathematical numbers are exact, but not necessarily aspects of the real world. I gather this is much of your thesis anyway. I agree.

    * has a repeating continued fraction representation. I won't explain what that is but the Wiki article's pretty good.

    Now the continued fraction representation of is , or "1; followed by all 2's." You can't get any more finite that that. That phrase completely characterizes as a continued fraction. There's no priority between decimals and continued fractions. It's just that one's taught in high school and the other in math major number theory class. They're both equally valid ways of representing a real number.


    3) Euclid's proof depends only on Peano arithmetic (PA). In terms of proof strength, PA is the same as ZF without the axiom of infinity. So a diehard finitest would accept the irrationality of . A finitist accepts the existence of each of 0, 1, 2, 3, ..., but not a completed set of them. You don't need a completed set of natural numbers to prove that the square root of 2 is irrational. It's a finitary fact, not an infinitary one.

    So far we've seen that both constructivists and finitists would have no problem accepting . If we informally rank real numbers based on believablity, the noncomputables are the most unblievable reals. Those are the numbers that genuinely encode an infinite amount of information. Next in believability are transcendentals like . They're computable, but they're mysterious. Their existence wasn't even proven till the 1840's.

    The most believable irrationals are simple algebraic numbers like . Numbers that are the roots, or zeros, of polynomials with integer coefficients like . Those are super-easy to construct without using infinitary methods; and as the quadratic formula from high school shows, the ones that are the roots of quadratic polynomials are easy to determine.





    * lives in a finite extension of the rationals. This is the abstract algebraic approach I've talked about recently in another thread.

    But there's a much more down to earth way to explain this point. The idea is to view our ever-expanding number systems as the solution to the problem of solving some type of equation.

    So in the beginning (again this is thematic, not necessarily historical) we have the positive integers 1, 2, 3, ... We can solve equations like with no problem, the answer is .

    But what if we try to solve ? We're stuck. We haven't got a number to solve this equation. So we invent one. In fact we invent zero and all the negative integers just so we can now solve more equations.

    Now later on this invention gets formalized into the abstract algebra that I've presented. But the essential idea is just solving as many equations as we can, even if we have to make up numbers to do it. And over time, everyone comes to believe in these made up numbers.

    So ok, now someone gives us the equation . Now we're stuck, there's no integer, positive or negative, that will work. So we have to invent the rational number to solve the equation.

    So @Meta you see that the rational numbers, which you think are so sacred, are themselves just made-up fictions that at one time were controversial and not widely believed in.

    Ok now we have the rationals. What do we do with an equation like ? We have to invent ; and by extension all of the other real numbers of the form where .

    Now of course we need to solve and all the other quadratics; and we have to solve all the third degree equations, and so forth. There is a class of real numbers called the algebraic numbers that contains all the solutions of all the polynomial equations.

    It's tricky though because what about the simple quadratic ? We have to invent a new kind of number, the imaginary unit and the complex numbers, the set of all where and are real.

    And this process keeps going. There are quaternions and octonians and sedonians and more. There are weird numbers like the p-adics. There are Cantor's tranfinite ordinals and cardinals. There are matrices and tensors, beloved by the physicists.

    Every time mathematicians need a new kind of number they invent one; and then after a passage of time, people come to believe in these new numbers.

    There was a time when people believes in the integers but not the rationals. You believe in the rationals but not the irrationals. But there's nothing special about the rationals. They were once a fiction too. Your choice is arbitrary and not based on anything but the era in which you were born, and your level of mathematical education.


    which as I argued above is bad.Metaphysician Undercover

    But no. It's not bad. It just is. And remember, if you lived in a different age you'd think negative numbers were bad. Then you'd think zero is bad. Then you'd think rational numbers are bad.

    Your feeling about what numbers are real and which aren't is purely a matter of accident based on the age you live in and your level of mathematical knowledge.

    I hope you can get outside yourself to get this point. There's nothing special about the rational/irrational jump. It's one jump in a long historical line of mathematical sophistication from putting a mark on a cave wall every time you kill a mastodon; to doing the most advanced research mathematics and phyiscs. You can't draw a line that says this step is real and the next step isn't. The rationals are just as fake -- or just as real -- as the irrationals.

    So it's not "bad" that is irrational. It just is. Some numbers are rational and some are integers and some are p-adics and some are quaternions. Mathematicans have lots and lots of numbers. They all have mathematical existence.

    This makes the square a truly impossible ...Metaphysician Undercover

    Of course a unit square is not impossible, it's the most obvious geometric figure there is after the equalateral triangle. Speaking of which, an equalateral triangle with sides of 1 has an altitude of . Can't avoid those pesky irrationals, they are literally all over the place. Everywhere you look.

    But to say a square is "impossible" simply because you don't like the great discovery of Pythagoras ... that seems a little beyond the pale for serious discourse in my opinion.


    , or irrational figure.Metaphysician Undercover

    Equivocating irrational as in "not a ratio [of integers]" with irrational as in cray-cray. Come on, man, you can do better than that.

    If the sides of a square are rational the diagonals are irrational. Man get over it. It just is, like the sun rising in the east. A fact about the world. That's one of the curious things about abstractions. Even though we make them up in our minds, they still bear definite truth values. 5 is prime even if you don't believe in the Platonic existence of 5. As a philosopher of math you need to account for that, not deny it because you don't like the Pythagorean theorem.

    And, all "powers" are fundamentally derived from the square.Metaphysician Undercover

    I'm not sure what you mean but from what follows I'm guessing you mean squares, cubes, hypercubes, and in general n-cubes; which, by the way, are perfectly well understood in math.

    Therefore any exponentiation is fundamentally unsound in relation to a spatial representation..Metaphysician Undercover

    That's just silly. There's nothing fundamentally unsound. The diagonal of a unit square can't be expressed as a ratio of integers. It's just a fact. It doesn't invalidate math. Even the Pythagoreans threw someone overboard then accepted the truth.

    The tl;dr on all this is that you're just mistaken that there's anything special about rational numbers, other than the fact that (by definition) they're ratios of integers. Lots of naturally occuring mathematical constants turn out to be irrational.

    Among the irrationals, the very simplest are the quadratic irrationals like , meaning that they're roots of quadratic equations. They're so easily cooked up using basic algebra, or Turing machines, or continued fractions.

    The bottom line is that your unfamiliarity with certain aspects of math is leading you to philosophical errors. has a very strong claim to mathematical existence and it's a finitary object, not an infinitary one. Likewise is computable, hence encodes only a finite amount of information. Decimal representation is not determinative of a real number's infinitary nature.
  • What is the difference between actual infinity and potential infinity?
    @Meta,

    I've read through much if not most of your writings in this thread. I think I understand where you're coming from. I found two remarks I can get some traction on.


    From my perspective, ZFC has unsound axioms concerning the nature of objects, as we discussed earlier. Therefore any proof using ZFC is unsound.Metaphysician Undercover

    ZFC is unsound. Well yes. Of course ZFC is unsound. Its deductions are valid, meaning that each theorem follows from the axioms and prior theorems according to the purely syntactic rules of deduction.

    But it's unsound, in the sense that its premises are not necessarily true. It's not even clear that they are meaningful. Personally I don't think they are. I don't personally believe that sets, as understood in ZFC, exist in the real world. You're arguing that they don't but of course they don't. I'm in total agreement with you on this point.

    I'll go you one better. ZF is unsound. No need to invoke the axiom of choice. In ZF we have the axiom of infinity, which states that there is an infinite set. Nothing in the physical world corresponds to that as far as we know. So ZF is unsound.

    So ok. ZF[C] is unsound. This is a commonplace observation. Might you be elevating it to a status it doesn't deserve? Are you thinking of it as an endpoint of thinking? What if it's only the beginning of philosophical inquiry?

    Here's what Bertrand Russell, who knew a thing or two about both mathematics and philosophy, said in 1910. This quote is usually given as a one-liner but the entire paragraph deserves repeating.

    “Pure mathematics consists entirely of assertions to the effect that, if such and such a proposition is true of anything, then such and such another proposition is true of that thing. It is essential not to discuss whether the first proposition is really true, and not to mention what the anything is, of which it is supposed to be true. [...] Thus mathematics may be defined as the subject in which we never know what we are talking about, nor whether what we are saying is true. People who have been puzzled by the beginnings of mathematics will, I hope, find comfort in this definition, and will probably agree that it is accurate.” — Uncle Bertie

    https://www.goodreads.com/quotes/577891-pure-mathematics-consists-entirely-of-assertions-to-the-effect-that

    Since this understanding is over a century old, it seems reasonable to take it as a starting point for the study of the philosophy of mathematics; and not the endpoint, as you have done. Mathematics is not literally true. It's a language for expressing physical theories; and it's a discipline unto itself that must be taken on its own terms.

    Let's take Russell's quote one step farther. In 1960 the physicist Eugene Wigner published an article called, The Unreasonable Effectiveness of Mathematics in the Natural Sciences.

    The title says it all. Mathematics is so fundamentally divorced from reality that it is unreasonable that it should have anything to tell us about the real world.

    And yet it does.

    That, I submit, is one of the key issues of the philosophy of math. We agree that math isn't true, but it nevertheless seems intimately related to the real or the actual.

    This is what I mean when I say that "ZCF is unsound" is the starting point of philosophical inquiry into the nature of mathematics; not the end of it. I get the feeling you think it's the last word. It's only the first.

    Next: Part 2.
  • How big will the blood bath be when the economy flips?
    In Facebook groups on the 2nd Amendment and gun control, guys now say things like they want to masturbate when someone gets their face blown off, and get liked for it.ernestm

    Look at the national orgy of bloodlust when the US kills some Iranian general whose name you never heard of yesterday. Bloodlust is popular these days. Plus you seem to be cherry picking bad stuff. I have a very wide range of online reading, sites many decent people won't go near, and I've never seen extreme stuff like that. Perhaps you should stop going looking for trouble.

    When the economy crashes most people will be fine and some will have to move in with relatives or whatever. The media have an interest in keeping you hysterical. Don't play along.
  • My own (personal) beef with the real numbers
    Human beings may have gotten over this, but they did not resolve the problem.Metaphysician Undercover

    The context is that "this" is the discovery by the Pythagoreans that for any pair of integers, the ratio of their squares can not be 2.

    @Meta as I mentioned I've been working on a response to something you wrote in the bijection thread, and I'm taking my time to sort out my thoughts. In fact many of my ideas have been leaking into my recent posts; and clearly I've spilled the beans that it's your paragraph about Pythagoras that really caught my eye.

    I have a lot to say on the subject of the square root of 2 and I don't want to say it all here. I'll keep my remarks here brief, and please be aware that I am going to offer a more detailed response to your point about Pythagoras soon.

    Consider the problem this way. Take a supposed "point". Now measure a specific distance in one direction, and the same distance in a direction ninety degrees to the first. Despite the fact that you use the exact same scale of measurement, in both of these measurements, the two measurements are incommensurable. Why is that the case?Metaphysician Undercover

    Because not every number that pops up naturally is rational. This is just a fact of life. I could push a philosophical point and say it's a fact of nature; and that some mathematical facts, abstract though they may be, are nevertheless forced on us somehow; and that it's the job of the mathematical philosopher to figure out how that miracle occurs. 5 is prime even though there is no 5 and there aren't any primes. It's not fiction. We can make up our own math but some things are not negotiable. There are mathematical truths. "5 is prime " is one; "the square root of 2 is irrational" is another.

    But your stance here is literally pre-Pythagorean. The Pythagoreans threw some guy overboard for making the discovery, but they accepted the fact of the irrationality of . You refuse even to do that. You're entitled to your own ideas, but to me that is philosophical nihilism. To reject literally everything about the modern world that stems from the Pythagorean theorem. You must either live in a cave; or else not live at all according to your beliefs. You must reject all of modern physics, all of modern science and technology. You can't use a computer or any digital media. You are back to the stone age without the use of simple algebraic numbers like .

    Doesn't this tell you something about the thing being measured (space)?Metaphysician Undercover

    No of course not. It tells me something interesting about abstract, idealized mathematical space. It tells me nothing about actual space in the world. Since all measurement is approximate, even in classical physics, we can certainly take all physical measurements to be rational numbers if you like. It's ok by me. There are no irrational distances in physical space for the simple reason that there are no exact distances at all that we can measure. So it's not meaningful to talk about them except in idealized terms.

    Math Physics. When you get that you will be englightened.

    What it tells me, is that this thing being measured (space), cannot actually be measured in this way. The irrational nature of pi tells us the very same thing. Two dimensional objects have a fundamental problem which demonstrates that space cannot actually be represented in this way.Metaphysician Undercover

    You're confusing physical measurement of the real world, with abstract idealized lengths in mathematics. It's an elementary error, easily corrected. Especially now that I've corrected it for you.


    We see a very similar problem in the relation between zero dimensional figures (points), and one dimensional figures (lines), as discussed in the other thread. So if we get done to the basics, remove dimensionality and focus solely on numbers, we can learn to understand first the properties of numbers, quantity, and order, without applying any relations to spatial features. Then we can see that it is only when we apply numbers to our dimensional concepts of space, that these problems occur. The problems result in establishing a variety of different number systems mentioned in this thread. None of these numbers systems has resolved the problem because the problem lies within the way that we model space, not within any number system. We do not have a representation of space which is compatible with numbers.Metaphysician Undercover

    That's a little word-salady for my taste. Couldn't parse it. But I gather from your Pythagoras paragraph in the bijection thread that you object to n-dimensional Euclidean space as well, for the same reason. It logically follows that if you don't like irrational distances you wouldn't like the n-dimensional Euclidean distance formula, so I don't think this is a separate issue.

    As I say I am working on a more comprehensive response to your Pythagorean lament, which will be forthcoming soon. Meanwhile let me just note some key points.

    * only encodes a finite amount of information. It's true that its decimal representation is infinite, but that's an artifact of decimal representation. There are many finite characterizations of .

    * It's computable, so its decimal digits can be completely described by a finite-length computer program. Therefore a constructive mathematician would accept its existence and properties.

    * It's algebraic, so it can be realized in a finite extension field of the rational numbers, . I outlined this mathematical construction in the second half of this post ... https://thephilosophyforum.com/discussion/comment/368048

    * Euclid's proof of the irrationality of requires only PA (Peano aritmetic) and not ZF. Therefore a mathematical finitist would accept its existence. The last time I tried to explain the Peano axioms to you, you were so triggered by a little symbology that you were unable to engage. I hope you'll grow past that. You can't be a philosopher of math without rolling up your sleeves and dealing with a little symbology now and then.

    * has a continued fraction representation of . In other words it has a repeating pattern that can be described finitely: "one followed by all 2's."

    For all these reasons, is essentially a finite mathematical object. You're simply wrong that it "introduces infinity," because you have only seen some bad high school teaching about the real numbers. Decimal representation is only one of many ways to characterize , and all the other ways are perfectly finite.

    Finally, if you said, "Math says there are noncomputable real numbers and that must be nonsense," I would still disagree with you but you would still have a much stronger case. All the constructivists and neo-intuitionists would agree with you. That argument would have the benefit of being a sophisticated attack on standard set theory.

    But to simply say that you don't like ; that's just a hopelessly naive viewpoint. shows up in many different finite constructions, from Turing machines to continued fractions to finite degree extension fields in abstract algebra.

    has very solid mathematical existence. You're simply wrong that it doesn't.

    If you said that you don't like noncomputables you'd have a better case. And if you said you don't like transcendentals, you'd still be wrong but it would be a slightly better case. But to reject the mathematical existence of a harmless algebraic number like is just a lack of sufficient mathematical understanding. You have no defensible philosophical point. It's too easy to construct by finitary means. Like ... um ... the diagonal of a unit square.

    Well actually those were most of the points I'm making in my post-to-be. Most of it's just drilldown of these bullet points. Maybe I'm done now. I'll have to go back and look.

    Let me ask a larger question. Is it mathematical abstraction that bothers you? Of course there's no physical length that can be measured as . But there's no physical length that can be measured as 1 either. Don't you know that?

    Two dimensional objects have a fundamental problem which demonstrates that space cannot actually be represented in this way.Metaphysician Undercover

    I just noticed this. It's the heart of your confusion. A representation is not the thing itself. We can and do "represent" space as the real line or pi or whatever. But we don't actually think space IS that mathematical representation. It's just a representation, imperfect from the start. It's an approximation at best, a convenient lie at worst.

    Everybody knows this. Or at least I know this. And now that you know I know this, maybe you'll stop holding me responsible for opinions I don't hold. Your argument is with someone else.

    ps -- Tegmark's wrong. Is this what you're on about? The world isn't literally math. A representation of reality is not reality. The map is not the territory. And not even Tegmark takes his own idea seriously, as witnessed by his rapid retreat from the mathematical universe hypothesis to the computable universe hypothesis, which is actually inconsistent with known physics. Don't worry about people who say the physical world "is" math. The physical world is only represented by math. Not the same thing.

    It's feeding time in my vat now.
  • Mathematicist Genesis
    And the joint negation or complement operation is the sole sufficient operation, which returns the set of everything that is not any of the arguments fed into iPfhorrest

    Buzz. Wrong. There's no universal set. Russell's paradox. You can't take the complement of the empt set except with respect to some given enclosing set.