There's something about modernity that is inimical to the traditional idea of wisdom. — Wayfarer
Like for example, when someone says "an empty set has no elements", and also says "the elements of the empty set A are the same elements as the elements of the empty set B". The former says the empty set has no elements, the latter states its negation "the elements of the empty set...".A contradiction is the conjunction of a statement and its negation. — TonesInDeepFreeze
A philosophy crank is more like it. You have zero familiarity with the 20th century literature on the philosophy of set theory. You haven't read Maddy, Quine, or Putnam. You have no interest in learning anything about the philosophy of set theory. When I mentioned to you the other day that Skolem was skeptical of set theory as a foundation for math, you expressed no curiosity and just ignored the remark. Why didn't you ask what his grounds were? After all he was one of the major set theorists of the early 20th century. — fishfry
Mine is the perfectly standard interpretation, comprehensible to everyone who spends a little effort to understand it. Two sets are the same if and only if they have the same elements. Formally, if a thing is in one set if and only if it's in the other; which (as we will shortly see) includes the case where both sets are empty. — fishfry
Are you saying that two things can be "the same" but not equal? Are you sure whatever you're on is legal in your jurisdiction? — fishfry
In other words "If 2 + 2 = 5 then I am the Pope" is a true material implication. Do you understand that? Do you agree? Do you have a disagreement perhaps? — fishfry
Now I claim that for all XX, it is the case that X∈A⟺X∈BX∈A⟺X∈B. That is read as, "X is an element of A if and only if X is an element of B.
In sentential logic we break this down into two propositions: (1) If X is an element of A then X is an element of B; and (2) If X is an element of B then X is an element of A."
Now for (1). If X is a pink flying elephant, then it's a person on the moon. Is that true? Well yes. There are no pink flying elephants and there are no people on the moon. So this is line 4 of the truth table, the F/F case, which evaluates to True. So (1) is true. — fishfry
I just gave you a formal proof to the contrary. An object is in A if and only if it's in B. If A and B happen to be empty, that is a true statement. — fishfry
You interpret your own ignorance as deception by others. Pretty funny. — fishfry
For purposes of this discussion, we take the two predicates as absolute and not contingent. You're just raising this red herring to sow confusion. The only one confused here is you. — fishfry
So, we're, in our "ordinary" lives, stuck with rules that are neither justified to our satisfaction nor universal in scope. — TheMadFool
What if, in keeping with Wittgenstein's ludological analogy, rules are more about making the "game" more fun, more interesting and less about justification? In other words, rules don't need to be justified in that they have to make sense, instead they have to ensure the "game" is enjoyable, exciting, and pleasurable but also "painful" enough to, ironically, make the "playing" the "game" a serious affair. — TheMadFool
. It's exactly like chess. I'm teaching you the rules. If you don't like the game, my response is for you to take up some other game more to your liking. — fishfry
But I have already explained to you in my previous post, that "a set is characterized by its elements" is merely an English-language approximation to the axiom of extentionality, which actually says, — fishfry
That is the axiom that says that two sets are equal if they have exactly the same elements. And by a vacuous argument -- the same kind of argument that students have had trouble with since logic began -- two sets are the same if they each have no elements. — fishfry
The formal symbology is perfectly clear. And even if it isn't clear to you, you should just accept the point and move on, so that we can discuss more interesting things. — fishfry
What's true is that given any thing whatsoever, that thing is a pink flying elephant if and only if it's a person on the moon. So the axiom of extensionality is satisfied and the two sets are equal. If you challenged yourself to work through the symbology of the axiom of extentionality this would be perfectly clear to you. — fishfry
The axiom of specification allows us to use a predicate to form a set. The predicate is not required to have a nonempty extension. — fishfry
Of course not. It's not a matter of cardinal equivalence. The elements themselves have to be respectively equal. — fishfry
Of course not. It's not a matter of cardinal equivalence. The elements themselves have to be respectively equal. {1,2} and {1,2} are the same set. {1,2} and {3,47} are not. — fishfry
The axiom of extensionality tells us when two sets are the same. — fishfry
You are right about that. But that's because we are making up examples from real life. Math doesn't have time or contingency in it. 5 is an element of the set of prime numbers today, tomorrow, and forever. The "people on the moon" example was yours, not mine. I could have and in retrospect should have objected to it at the time, because of course it is a temporally contingent proposition. I let it pass. So let me note for the record that there are no temporally contingent propositions in math. — fishfry
This says in effect that if two sets have exactly the same elements, they're the same set. But the way it's written, it also includes the case of a set with no elements at all. If you have two sets such that they have no elements, they're the same set; namely the empty set. — fishfry
Another point is that everyone has trouble with vacuous arguments and empty set arguments. If 2 + 2 = 5 then I am the Pope. Students have a hard time seeing that that's true. The empty set is the set of all purple flying elephants. A set is entirely characterized by its elements; and likewise the empty set is characterized by having no elements. John von Neumann reportedly said, "You don't understand math. You just get used to it." The empty set is just one of those things. You can't use your common sense to wrestle with it, that way lies frustration. — fishfry
Every set is entirely characterized by its elements. — fishfry
The set of pink flying elephants is an empty set. The set of people on the moon is an empty set. And the axiom of extensionality says that these must be exactly the same set. — fishfry
There is only one empty set, because the axiom of extensionality says that if for every object, it's a person on the moon if and only if it's a pink flying elephant, that the two sets must be the same. — fishfry
We know from the law of identity that everything is equal to itself. So what is the set of all things that are not equal to themselves? It's the empty set. And by the axiom of extensionality, it's exactly the same as the set of pink flying elephants and the people on the moon. — fishfry
You are confusing the axiom of extension, which tells us when two sets are the same, with the other axioms that give us various ways to build sets or prove that various sets exist. — fishfry
When, for example, Metaphysician Undercover repeatedly misunderstands certain notions in mathematics, there is a point at which one concludes that he is simply not participating in the game. One might then either turn away or attempt to follow the path of the eccentric. The question becomes one of what is to be gained in going one way or the other. — Banno
What's trivial is saying that the Vitali set is "specified" because all its elements are real numbers. That's like saying the guests at a particular hotel this weekend are specified because they're all human. It's perfectly true, but it tells you nothing about the guests at the hotel. That's why your point is trivial. — fishfry
A set is entirely characterized by its elements. — fishfry
Some sets are specified by predicates, such as the set of all natural numbers that are prime. — fishfry
"By reference?" No. The Vitali set is characterized by its members, but I can't explicitly refer to them because I don't know what they are. It's a little like knowing that there are a billion people in China, even though I don't know them all by name. — fishfry
On the contrary. Since everything is equal to itself, the empty set is defined as {x:x≠x}{x:x≠x}. I rather thought you'd appreciate that, since you like the law of identity. The empty set is in fact the extension of a particular predicate. — fishfry
The empty set is the extension of the predicate x≠xx≠x. Or if you like, it's the extension of the predicate "x is a purple flying elephant." Amounts to the same thing. — fishfry
Since the empty set is the extension of a particular predicate, your point is incoorect. — fishfry
I don't know what you're doing. i don't know what your point is.
...
I can't really follow your logic. — fishfry
If as you agree, all sets in standard set theory are composed of nothing but other sets; and that therefore every nonempty set whatsoever can be said to have elements that are sets; then isn't the fact that the elements of any set have in common the fact that they are sets, a rather trivial point? — fishfry
All multiverse theories fail at their core, because they are pure speculation without evidence. — Philosophim
We are at an impasse. — Fooloso4
The real numbers include some numbers that are in VV and many that aren't. In what way does that specify VV? That's like saying I can specify the people registered at a hotel this weekend as the human race. Of course everyone at the hotel is human, but humanity includes many people who are not registered at the hotel. — fishfry
How so? — fishfry
And the people at the hotel are humans. As are all the people not at the hotel. If that's all you mean by specification, that all I have to do is name some arbitrary superset of the set in question, then every set has a specification. If that's what you meant, I'll grant you your point. But it doesn't seem too helpful. It doesn't tell me how to distinguish members of a set from non members. — fishfry
First, the elements of a set need not be "the same" in any meaningful way. The only thing they have in common is that they're elements of a given set. — fishfry
The elements of a set need have no relation to one another nor belong to any articulable category or class of thought, OTHER THAN being gathered into a set. — fishfry
There is no need for outside agency. This view is much closer to our scientific understanding of physiology and homeostasis. — Fooloso4
It is not a correction, it is a different concept of the soul. It is a soul that is completely separate from the body. — Fooloso4
The argument is as follows: soul is an attunement, vice is lack of attunement, and so the soul cannot be bad and still be a soul because it would no longer be an attunement. What is missing from the argument is that being in or out of tune is a matter of degree. Vice is not the absence of tuning but bad tuning. — Fooloso4
You previously denied that something can be more or less in tune, but, as any musician or car mechanic can tell you, that is simply not true. — Fooloso4
The problem with 94c is that there is such a thing as singing out of tune, internal conflict, acting contrary to your own interests, and so on. — Fooloso4
In the Republic passions and desires are in the soul. It is a matter of one part of the soul ruling over the other parts of the soul. Why does Socrates give two very different accounts of the soul? Does the soul have parts or not? Are desires and anger in the soul or in the body? Why would he reject attunement in the Phaedo and make it central to the soul in the Republic? — Fooloso4
. In addition to those above there is the problem of the identity of Socrates himself. — Fooloso4
So ∼∼ partitions the real numbers into a collection of pairwise disjoint subsets, called equivalence classes, such that every real number is in exactly one subset. By the axiom of choice there exists a set, generally called VV in honor of Giuseppe Vitali, who discovered it, such that VV contains exactly one member, or representative, of each equivalence class. — fishfry
You're wrong. I just demonstrated a specific example, one that is not only famous in theoretical mathematics, but that is also important in every field that depends on infinitary probability theory such as statistics, actuarial science, and data science.
I know you have an intuition. Your intuition is wrong. One of the things studying math does, is refine your intuitions. — fishfry
You can tell me NOTHING about the elements of VV. Given a particular real number like 1/2 or pi, you can't tell me whether that number is in VV or not. The ONLY thing you know for sure is that if 1/2 is in VV, then no other rational number can be in VV. Other than that, you know nothing about the elements of VV, nor do those elements have anything at all in common, other than their membership in VV. — fishfry
Still Metaphysician Undercover must also agree that when he says that @jgill and I have infinite regress wrong, he's incorrect about that too. If both interpretations are the same, everyone's right. — fishfry
he is not talking about some invisible act. The tuning of what is tuned is not the act of tuning, but rather the result. — Fooloso4
There is in this theory no outside agent or principle acting: — Fooloso4
The tuning is not the act of tuning, it is the ratio of frequencies according to which something is tuned. — Fooloso4
The cause of the lyre being in tune is not the activity of tightened and slackens the strings. If I give you a lyre you cannot tune it unless you know the tuning, unless you know the ratio of frequencies. It is in accord with those ratios that the lyre is in tune. The cause of the lyre being in tune is Harmony. — Fooloso4
Whether the body requires something else acting on it is never discussed. — Fooloso4
I looked at the SEP article. That is utterly bizarre. An infinite regress goes backward without a beginning. Going forward without end like the Peano axioms is not an infinite regress. — fishfry
I agree. It's nonsense. Regress means going backward. I am more than familiar with these notions, as I investigate dynamical processes going forward as well as those going backward. — jgill
But MOST sets can't possibly have specifications, because there are more sets than specifications, a point I've made several times and that you prefer not to engage with. There are uncountably many sets and only countably many specifications. There simply aren't enough specifications to specify all the sets that there are. Most sets are simply collections of elements unrelated by any articulable property other than being collected into that set. — fishfry
The tuning is not the thing that is tuned. The tuning is the octave, 4th, and 5th, the ratios according to which the strings of a lyre are tuned. Analogously, the tuning of the parts of the body too is in accord with the proper ratios. Again, the tuning should not be confused with the body that is tuned. — Fooloso4
Harmonia here does not mean a harmony in the sense of melodious sound, but the state of the lyre, brought about by a combination of things, that enables it to produce a certain sound: — Apollodorus
But now it seems that there might be an alternative. Rather than an incomplete yet consistent account of mathematics and language, we might construct an inconsistent yet complete account... — Banno
Peano’s axioms for arithmetic, e.g., yield an infinite regress. We are told that zero is a natural number, that every natural number has a natural number as a successor, that zero is not the successor of any natural number, and that if x and y are natural numbers with the same successor, then x = y. This yields an infinite regress. Zero has a successor. It cannot be zero, since zero is not any natural number’s successor, so it must be a new natural number: one. One must have a successor. It cannot be zero, as before, nor can it be one itself, since then zero and one would have the same successor and hence be identical, and we have already said they must be distinct. So there must be a new natural number that is the successor of one: two. Two must have a successor: three. And so on … And this infinite regress entails that there are infinitely many things of a certain kind: natural numbers. But few have found this worrying. After all, there is no independent reason to think that the domain of natural numbers is finite—quite the opposite. — Stanford Encyclopedia of Philosophy
The soul, according to his argument, brings life to the body. — Fooloso4
[His response to Simmias' argument is that you can't have it both ways. You can't have both the soul existing before the body and the soul being a harmony of the parts of the body.] — Fooloso4
Right. In this case the Form would be Harmony. Just as a beautiful body is beautiful by the Beautiful, the harmonious body is harmonious by the Harmonious. — Fooloso4
I think you are being taken for a ride. There is no "Form of Harmony". — Apollodorus
There is no “Form of Harmony” in Plato for the simple reason that what we call “harmonious” in Modern English, is “rightly-ordered” or “just” (depending on the context) in Plato. So, the corresponding Form would be Justice, not “Harmony” which does not exist.
In Plato, the proper functioning of a whole, be it a city or a human, is not harmony but justice or righteousness (dikaiosyne). Dikaiosyne is the state of the whole in which each part fulfills its function: — Apollodorus
But we're not talking "fact," if by that you mean the real world. The subject was set theory, which is an artificial formal theory. Set theory is not any part of any physical theory. I pointed out to you that in set theory, everything is a set, including the elements of sets. You responded by saying you hadn't realized that. I thought we were therefore making progress: You acknowledged learning something you hadn't known before. And now you want to revert back to "fact," as if set theory has an ontological burden. It does not. — fishfry
Focus. You said that the fact that in set theory everything is a set, leads to infinite regress. I pointed out that the negative integers are an example of an unproblematic negative regress; and that the axiom of foundation rules out infinite regresses of set membership. — fishfry
Yes, that didn't last long. But you were more than agreeable the other day. You actually achieved some insight. You realized that a set has no definition, and that its meaning is derived from the axioms. You realized that the members of sets are also sets. — fishfry
So "2" cannot refer to two distinct but same things? — Luke
You cannot have 2 apples or 2 iPhones, etc? — Luke
The categories we use are either discovered or man-made. If they are discovered, then how can we be "wrong in an earlier judgement" about them; why are there borderline cases in classification; and why does nothing guarantee their perpetuity as categories? — Luke
First, there is no need for something to order the parts. If you assume that the parts together need to be ordered, then each part would also need to be ordered because each part of the body has an order. — Fooloso4
Second, in accord with Socrates' notion of Forms something is beautiful because of Beauty itself. Something is just because of the Just itself. Something is harmonious because of Harmony itself. Beauty itself is prior to some thing that is beautiful. The Just itself is prior to some thing being just. Harmony itself is prior to some thing being harmonious. In each case there is an arrangement of parts.
The question is, why did Socrates avoid his standard argument for Forms? It is an important question, one that we should not avoid. — Fooloso4
I'm missing your point also. What's your gripe about the innocuous Riemann sphere? :chin: — jgill
"2" can also refer to two distinct but same things, such as "things" of the same type or category. — Luke
But all categories/classifications are equally as fictitious and man-made as the sets and orders you reject. — Luke
Scientists justified both the inclusion and exclusion of Pluto as a planet at different times. Like Pluto, many individual "things" are borderline cases in their classification. Moreover, nothing guarantees the perpetuity of any category/set, or of what defines ("justifies") the inclusion of its members. — Luke
Furthermore, if you base your mathematics on empiricism rather than on "abstraction" or "fiction", then you must also reject fractions, since a half cannot be exactly measured in reality. — Luke
If there are "no real boundaries between things", then acknowledging that "anything observed might be divisible an infinite number of times" is not to "give up on the realism", but to adhere to it. — Luke
t is what he argues against. He does this by changing the terms of the argument. His argument is based on a pre-existing soul, something that is not part of Simmias' argument. — Fooloso4
How can either the number 2 or the numeral "2" represent or mean anything in use if no two things are identical in spatiotemporal reality? Isn't the law of identity the basis of your mathematics? — Luke
No not at all. First, what's wrong with infinite regress? After all the integers go backwards endlessly: ..., -4, -3, -2, -1, 0, 1, 2, 3, 4, ... You can go back as far as you like. I'm fond of using this example in these endlessly tedious online convos about eternal regress in philosophy. Cosmological arguments and so forth. Why can't time be modeled like that? It goes back forever, it goes forward forever, and we're sitting here at the point 2021 in the Gregorian coordinate system. — fishfry
jgill was referring to the Riemann sphere, a way of viewing the complex numbers as a sphere. It's based on the simple idea of stereographic projection, a map making technique that allows you to project the points of a sphere onto a plane. There is nothing mystical or logically questionable about this. You should read the links I gave and then frankly you should retract your remark that the Riemann sphere is a "vicious circle." You're just making things up. Damn I feel awful saying that, now that you've said something nice about me. — fishfry
Jeez Louise man. I say: "The only thing they have in common is that they're elements of a given set." And then you say I "ought to recognize ..." that very thing. — fishfry
A very disingenuous point. The elements of a set need have no relation to one another nor belong to any articulable category or class of thought, OTHER THAN being gathered into a set. — fishfry
Ok, you are now agreeing with me on an issue over which you've strenuously disagreed in the past. You have insisted that "set" has an inherent meaning, that a set must have an inherent order, etc. I have told you many times that in set theory, "set" has no definition. Its meaning is inferred from the way it behaves under the axioms. — fishfry
And now you are making the same point, as if just a few days ago you weren't strenuously disagreeing with this point of view.
But in any event, welcome to my side of the issue. Set has no definition. Its meaning comes exclusively from its behavior as specified by the axioms. — fishfry
Not at all. Bricks are the constituents of buildings, but all the different architectural styles aren't inherent in bricks. There are plenty of sets that aren't numbers. Topological spaces aren't numbers. The set of prime numbers isn't a number. Groups aren't numbers. The powerset of the reals isn't a number. Just because numbers are made of sets in the formalism doesn't mean every set is a number. — fishfry
Meta I find you agreeing with my point of view in this post. — fishfry
So you would ban the teaching of Euclidean geometry now that the physicists have accepted general relativity? — fishfry
Would you ban Euclidean geometry from the high school curriculum because it turns out not to be strictly true? — fishfry
There is no criterion. In fact there are provably more sets than criteria. If by "criterion" you mean a finite-length string of symbols, there are only countably many of those, and uncountably many subsets of natural numbers. So most sets of natural numbers have no unifying criterion whatsoever, They're entirely random. — fishfry
I just proved that most sets of natural numbers are entirely random. There is no articulable criterion linking their members other than membership in the given set. There is no formal logical definition of the elements. There is no Turing machine or computer program that cranks out the elements. That's a fact. — fishfry
According to Simmias' argument there is nothing prior to the body that directs its parts. The body is self-organizing. — Fooloso4
Right, and that is the problem with your argument. Not only do you assume that all the parts together must be arranged, but for the same reason each of the parts individually must be arranged. If the soul arranges all of the parts together what arranges each of the individual parts? It can't be the soul because then the soul would be the cause of the body. — Fooloso4
In this case he did more than just turn it around. Simmias' argument did not include a separate soul. Socrates does not deal with Simmias' argument because the result would be that the soul does not endure. — Fooloso4
Directing the parts does not mean creating the parts. The soul does not cause the body. — Fooloso4
Although, as Apollodorus pointed out to me, 'the argument from harmony' is actually dismissed in the dialogue. — Wayfarer
Socrates’ argument does not depend on the pre-existence of soul. Even if the soul's pre-existence is not assumed, Simmias’ analogy still fails. — Apollodorus
That is not Simmias' argument. Note the following: — Fooloso4
That is not what Simmias' argument says. And according to Socrates' argument, the soul does not cause the body that is strung and held together by warm and cold and dry and wet and the like — Fooloso4
Since no two things are identical in spatiotemporal reality, do you also reject the number 2? — Luke
Sets can contain other sets. In fact a set is "something" in addition to its constituent elements. It's a "something" that allows us to treat the elements as a single whole. If I have the numbers 1, 2, and 3, that's three things. The set {1,2,3} is one thing. It's a very subtle and profound difference. A set is a thing in and of itself. — fishfry
The harmony is the tuning. — Fooloso4
The organic body is an arrangement of parts. They do not first exist in an untuned condition and subsequently become tuned. A living thing exists as an arrangement of parts. An organism is organized. — Fooloso4
The assumption is that the mind or soul exists independently of the body. That is what is in question. All of the arguments for that have failed. — Fooloso4
Yes, that is the argument, but it assumes the very thing in question, the existence of the soul independent of the body, that they are two separate things. (86c) The attunement argument is that they are not. But Simmias had already agreed that the soul existed before the body. It is on that basis that Socrates attacks that argument. In evaluating the argument we do not have to assume the pre-existence of the soul. — Fooloso4
In set theory everything is a set. — fishfry
Sets whose elements are sets whose elements are sets, drilling all the way down to the empty set. — fishfry
No, not at all. First, the elements of a set need not be "the same" in any meaningful way. The only thing they have in common is that they're elements of a given set. — fishfry
The concept of "set" itself has no definition, as I've pointed out to you in the past. — fishfry
There is no set of ordinals, this is the famous Burali-Forti paradox. — fishfry
There is no general definition of number. — fishfry
You see you're at best a part-time Platonist yourself. — fishfry
If I put on my Platonist hat, I'll admit that the number 5 existed even before there were humans, before the first fish crawled onto land, before the earth formed, before the universe exploded into existence, if in fact it ever did any such thing. — fishfry
I must say, though, that I am surprised to find you suddenly advocating for mathematical Platonism, after so many posts in which you have denied the existence of mathematical objects. Have you changed your mind without realizing it? — fishfry
But Meta, really, you are a mathematical Platonist? I had no idea. — fishfry
I agree with the points you're raising. I don't know if 5 existed before there were humans to invent math. I truly don't know if the transfinite cardinals were out there waiting to be discovered by Cantor, and formalized by von Neumann. After all, set theory is an exercise in formal logic. We write down axioms and prove things, but the axioms are not "true" in any meaningful sense. Perhaps we're back to the Frege-Hilbert controversy again. — fishfry
The first is true independent of any instrument. The second is true of a particular instrument. The first is about the ratio of frequencies. The second about whether those relations are achieved on a particular instrument. — Fooloso4
In the Republic the problem is not between the parts of the body and the soul but which part of the soul. The answer is reason. In addition, appetites are treated as a part of the soul and not the body. The conflict is within the soul, not between soul and body. Also the soul in the Republic has parts but in the Phaedo it is denied that it has parts. — Fooloso4
That incorrectly makes it appear that I said, "Incorrect: We should not use 'least' if we don't mean quantity." — TonesInDeepFreeze
