It is not any more a contradiction for a set to have more than one ordering than it is a contradiction for a person to own more than one hat. — TonesInDeepFreeze
Having X hat does not exclude having Y hat, that's obvious. The two do not contradict. But if X order contradicts Y order (e.g. John is closer to the front of the stage than Paul, contradicts Paul is closer to the front of the stage than John), then X order excludes Y order.
Your analogy is not relevant because having one property clearly does not exclude the possibility of having another property, but having the property of one order clearly contradicts having the property of the contradictory order.
I think it's time for you to go back to grade school and learn some fundamentals of logical thinking.
Set consisting of three balls colored red, white and blue. They also have differing weights. What is THE order? Just curious. — jgill
Show me your balls and I will tell you their order.
And exactly what order is that? — tim wood
However those objects relate to other objects, the context, or environment they are in, dictates their order.
Ok this is interesting. My quote was, "Sets are subject to the law of identity." So that if X is a set, I can say X = X without appealing to any principle of set theory.
Tones convinced me of that. Now you say that he only sophisted me. How so please? If X is a set, how is X = X not given by the law of identity? You have me curious.
You think I'm a victim of Tones's sophistry. That is an interesting remark. — fishfry
What is the case, is that "X=X" is an ambiguous and misleading representation of the law of identity. This is because "=" must mean "is the same as", to represent that law, but it could be taken as "is equal to". Notice that in the axiom of extensionality it is taken to mean "is equal to". Therefore when Tones takes "X=X" to be an indication of the law of identity there is most likely equivocation involved.
Set theory is a mathematical structure. The analogy is:
Set theory is to group theory as a particular set is to a particular group.
But a set is a mathematical structure too, since the elements of sets are other sets. — fishfry
So, do you recognize, and respect the fact that group theory is separate from, as a theoretical representation of, the objects which are said to be members of a specified "group"? And, I'm sure you understand that just like there is a theoretical representation of the group, there is also a theoretical representation of each member of the group. In set theory therefore, there is a theoretical "set", and also theoretical "elements".
So when Tones says that a set may consist of concrete objects, this is explicitly false, because the set is the theoretical representation, and the elements of the set are theoretical representations as well. Through such false assertions, Tones misleads people and earns the title of sophist.
When Tones speaks about the set "George, Ringo, John, Paul", these names signify an abstract representation of those people, as the members of that set, the names do not signify the concrete individuals. You, Fishfry, have shown me very clearly that you know this. So there is an imaginary "George", "Ringo" etc., which are referred to as members of the set. The imaginary representation is known in classical logic as "the subject". We make predications of the subject, and the subject may or may not be assumed to represent a physical object. Comparison between what is predicated of the subject, and how the object supposedly represented by the subject appears, is how we judge truth, as correspondence.
What is important to understand in mathematics, is that the subject need not represent an object at all. It may be purely imaginary, like your example Cinderella. This allows mathematicians to manipulate subjects freely, without concern for any "correspondence" with objects. Beware the sophist though. I believe that when the sophist says that the members of a set may be abstractions, or they may be concrete objects, what is really meant if we get behind the sophistry, is that in some cases the imaginary, abstract "element", may be assumed to have a corresponding concrete object, and sometimes it may not. Notice though, that in all cases, as you've been insisting in discussions with me, the elements of the sets are abstractions, as part of the theory, and never are they the actual physical objects. Failure to uphold this distinction results in an inability to determine truth as correspondence. And that is the effect of Tones' sophistry
This is true about kids in playgrounds, NOT mathematical sets. You have informed me that you don't like real-world analogies so I no longer use them. Mathematical sets have no inherent order. — fishfry
I'll return to the schoolkids example briefly to tell you why I didn't like it. Using that example made it unclear whether "schoolkids" referred to assumed actual physical objects, or imaginary representations. That's why "real-world analogies" are difficult and misleading. The names, "George", "Paul", etc., appear to refer to real-world physical objects, and Tones even claims that they do, but within the theory, they do not, they are simply theoretical objects. If we maintain the principle that the supposed "schoolkids" are simply imaginary, then they have no inherent order unless one is stipulated as part of the rules for creating the imaginary scenario. Set theory ensures that the elements have no inherent order, but this also ensures that the elements are imaginary.
A temporal extension. You are saying it only applies to things that exist in time? Meaning not sets? I don't think that's right. Any set is identical to itself and also equal to itself by virtue of the law of identity. — fishfry
This is wrong, and where Tones mislead you in sophistry. A set is not identical to itself by the law of identity. The set has multiple contradictory orderings, and this implies violation of the law of identity. We allow that "a thing", a physical object has contradictory properties with the principle of temporal extension. At one time the thing has a property contradictory to what it has at another time, by virtue of what is known as "change", and this requires time. But set theory has no such principle of temporality, and the set simply has multiple (contradictory) orderings.
Tones did explain that to me, but not via sophistry. He asked me to prove the transitivity of set equality. Once I attempted to do that, I realized that I needed not the axiom of extensionality, but its converse. And that converse is true by way of the law of identity from the underlying predicate logic. This I discovered for myself when Tones pointed me to it. — fishfry
As I said, the reference was to the identity of indiscernibles, not the law of identity. You recognize that these two are different. The proof was not by way of the law of identity. If you still believe it was, show me the proof, and I will point out where it is inconsistent with the law of identity.
I tell you that a set has no inherent order; and that the set of natural numbers in its usual order; and the set of natural numbers in the even-odd order say -- 0, 2, 4, 6, ...; 1, 3, 5, 7, ... is exactly the same set. It is a different ordered set, because in an ordered set, the order is part of the identity of the set. In a plain set, it's not. This is how mathematicians play their abstraction game. — fishfry
We agree on this very well. The principle we need to adhere to, is that this is always an "abstraction game". If we start using names like "Ringo" etc., where it appears like the named elements of the set are concrete objects, then we invite ambiguity and equivocation. And if we assert that the elements are concrete objects, like Tones did, this is blatantly incorrect.
Yes, well, discussions of denying LEM don't interest me much. I'll agree with that. But I've come by it honestly. I've made a run at constructivism and intuitionism more than once. I've read Andrej Brauer's "Five Stages of Accepting Constructive Mathematics." It doesn't speak to me. The paragraph you quoted is a little above my philosophical pay grade. Perhaps you can explain its relevance to the topic at hand. — fishfry
The three fundamental laws of logic, identity, noncontradiction, and excluded middle, are inextricably tied together. Therefore one cannot discuss identity without expecting some reference to the other two. There has been some philosophical discussion as to which comes first, or is most basic. Aristotle seemed to believe that noncontradiction is the most basic, and identity was developed to support noncontradiction.
What C.S. Peirce noticed, is that if we allow abstract objects to have "identity" like physical objects do, as Tones seems to be insisting on, then necessarily the validity of the other two laws is compromised. Instead of denying identity to abstract objects, as I do in the Aristotelian tradition of a crusade against sophistry, Peirce sets up a structure outlining the conditions under which noncontradiction, and excluded middle ought to be violated.
I don't see why. If X is a set, then X = X by identity. — fishfry
You are missing the point. The law of identity refers explicitly to things, "a thing is the same as itself". A "set" is explicitly a group of things. Therefore when you say X = X, and X is a set, rather than a thing, then "=" does not signify identity by the law of identity.
There is no time in set theory. Mathematics is outside of time, or talks about things that are outside of time. — fishfry
Right, this is the point. "Time", or temporal extension allows that a thing may have contradictory properties, at a different time, yet maintain its identity as the same thing, all the while. This is fundamental to the law of identity. Without time (as in mathematics), the multiple orderings of a set, which Tones referred to, are simply contradictory properties. That is a good example of the issue Peirce was looking at.
But given particular instances of set theory; that is, sets; we can ask if they are equal to each other or not.
So I promise not to say that the universe of sets is equal to the universe of sets. Though the category theorists will probably disagree with you. — fishfry
Fine, but can you respect the fact that "equal" does not imply "identical", despite the sophistical tricks that Tones is so adept at.
You are distorting what I said. ANY particular set is a particular instance of the concept of set, as any particular apple is an instance of the concept (or category) of apple. That causes no problem. — fishfry
No, that's simply wrong. A particular apple is a physical object. A set is an abstraction. An instance of an apple is a physical object. Your supposed "instance" of a set is an abstraction, a concept. The two are not analogous, and I argue that this is a faulty, deceptive use of "instance".
An instance is an example, and understanding of concepts or abstractions by example does not work that way. Assume the concept "colour" for example. If I present you with the concept "red", this does not provide you with an instance of the concept "colour". An instance of the concept "colour" would be the idea of colour which you have in your mind, or the idea of colour which I have in my mind, expressed through the means of definition. Each of those would provide you with an example of the concept of "colour", an instance of that concept. The concept "red" does not provide you with an example of the concept of "colour". Nor does a specific "set" provide you with an example or instance of the concept "set".
What you are saying in this case is completely mixed up and confused.