Talk:Identity of indiscernibles
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[edit] Confusion
This article handles the identity of indiscernibles and the indiscernibility of identicals together. The two are separate doctrines deserving separate articles. The indiscernibility of identicals, i.e., Leibniz's law, is indeed one of the two great metaphysical principles of Leibniz. The identity of indiscernibles is not one of the two great metaphysical principles of Leibniz, though Leibniz also accepted it (he thought it followed from the Principle of Sufficient Reason; he was probably wrong about that).
Moreover, it is crucial in the article to distinguish between the almost trivial version of identity of indiscernibles and the non-trivial. The almost trivial version is that if x and y have the same properties, they are identical, and this is how it is stated in the article. This version is easily shown to be true if one is liberal about what properties there are. Let P be the property of being identical with x. If x and y have the same properties, then because x has P, so does y. But then y is identical with x, since P is the property of being identical with x. To avoid such trivialization, the identity of indiscernibles needs to be restricted to purely qualitatively properties, i.e., ones that do not involve the existence of particular rigidly designated things, places, times, etc. It's hard to make this precise, but making it precise is necessary for stating the identity of indiscernibles.
I don't have the time for these revisions right now, but someone should do them. 141.161.84.89 20:23, 30 April 2007 (UTC)
[edit] Mention of duck
I'm going to delete this text:
So "if it looks like a duck, walks like a duck, and quacks like a duck, then it is a duck".
Why? Because the text is about classification, not about identity. This may be the case: If someone walks like a duck and quacks like a duck then that person is to be classified as a duck.
[edit] Controversial applications
what kind of fucking logic is this? the first 3 statements are about bill's world the conclusion is not!
we would be correct in concluding "bill believes 49/7 and the square root of 49 are two different things. And that is really how the world is!!!
Leibnitz was a genius. We have gone from an age of enlightenment to an age of darkness. We now live in a world of wikipedia half-wits RWS
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- I agree with you there, however you are raising a philosophical reply, some people do believe what is in the ariticle disputes Leibniz's law. Make a new section and call it replies if you want. --Aceizace 20:54, 19 February 2006 (UTC)
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- I think you are mistaken and the argument does not raise a valid philosophical reply. Note what you think problem with the argument is : “"bill believes 49/7 and the square root of 49 are two different things” à and therefore “And that is really how the world is!!!” This is EXACTLY the point the criticism is trying to make. The critique says that if we accept “identity of indiscernible” (Leibniz’s law) we will be led into absurd proposition that what Bill thinks makes the world that way. And since this is absurd(“what kind of fucking logic is this?” being your quote) the Leibnitz’s law is wrong.
- The correct response to this attack on leibnitz’s law is to claim that what a person thinks about the object is not the property of an object.--Hq3473 04:12, 20 February 2006 (UTC)
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- I just stumbled across this page and I also found the argument found in this section to be, uh, weak. I'll try to express it a little more mathematically.
- The claim in step 6 is that "
is not identical to
is absurd". - This is not absurd. They *aren't* identical. One has a 7 and a horizontal line, the other has a line with a bunch of corners. Just looking at them you can see that they are different.
- To be more precise,
" and
mathematical expressions, and they are *different* expressions. - In some contexts, these expressions reduce to the same integer, but in others they don't. For example, if the default base is hexidecimal instead of decimal, these expressions yeild different numbers, neither of which is an integer. In other contexts, not all operators are defined, which is what is going on with poor Bill. Once you introduce some more complicated operations, Gödel's incompleteness theorems shows that even if you know how to preform all operations and have a well defined context, there exists two expressions that are equal, but that you can not prove that they are equal. (Also see the halting problem.)
- It is important to distinguish between "identical" and "equivalent (under some context)".
- So, on a very simplistic visual level, you can see that
is not identical to
, and on a much higher mathematical level you can understand that, indeed, determining if two expressions are the same can be a very hard problem. It is only fairly basic formulas that people automatically do the reductions and mentally classify them as "the same" and then make the incorrect leap to thinking they are "identical". Wrs1864 05:21, 18 November 2006 (UTC)
- I changed this to a different example that does not involve evaluating math expressions, but presreves the basic problem of imperfect knowledge.--Hq3473 20:22, 18 November 2006 (UTC)
- Thanks, I like your example *much* better. I think it is proably a good idea to leave the dispute tag for a little while to make sure that others agree, but as far as I'm concerned, my objections have been satisfied. Wrs1864 03:56, 19 November 2006 (UTC)
- I changed this to a different example that does not involve evaluating math expressions, but presreves the basic problem of imperfect knowledge.--Hq3473 20:22, 18 November 2006 (UTC)
[edit] Leibniz?
I find it strange that Descartes lived and wrote Meditations before Leibniz was around, yet even the article itself says that Descartes used this reasoning. Might someone who knows more be able to include an explanation on why it is attributed to Leibniz? --Aceizace 20:54, 19 February 2006 (UTC)
- The principle existed LONG before Descartes, probably can be attributed to Plato. His theory of Forms had a similar concept. The law got called Leibniz law, for his formulation not for content. Therefore it is not weird that Descartes uses the principle before Leibniz formulation.--Hq3473 15:34, 23 February 2006 (UTC)
[edit] From Subjective to Objective
This principle of the identity of indiscernibles makes the claim that a subjective judgment is to be taken as correctly describing the objective world. It claims that what appears to one person has true being for everyone. Perception is reality. However, that is precisely the problem that is to be solved by almost all philosophy. Kant's whole philosphy was written in order to determinine the correctness of assuming that subjective opinions are objective. Einstein's Relativity is also about the subjective observer and his experience of objects. Berkeley, Schopenhauer, Descartes, and many others have dealt with subjectivity and its relation to objectivity. For Leibniz to proclaim the identity of indiscernibles was, itself, an attempt to assert that his own subjective observations should be considered as being truly descriptive of the objective world of experience.Lestrade 01:43, 3 June 2006 (UTC)Lestrade
- Feel free to edit the article acordingly. And do not forget to site your sources!--Hq3473 18:15, 7 June 2006 (UTC)
- No, it does not make that claim. It does not say "seem to have all the same properties", it says "have all the same properties". It does not presuppose being able to observe all those properties; indeed, with our knowledge of modern physics (Heisenberg's uncertainty principle) we know that one can't observe all properties at the same time. But that doesn't affect the correctness of Leibniz's claim, which is a definitional claim not a claim about human observations. greenrd 01:52, 15 February 2007 (UTC)
- Sure, i agree, in my understanding identity of indiscernibles is a metaphysical principal rather then epistemological one, but if someone find sites of famous philosophers thinking otherwise, the article should reflect it. --Hq3473 03:46, 15 February 2007 (UTC)
- According to greenrd, Leibniz is making a dogmatic, ontological,objective assertion about the way that the world is constituted, rather than a hypothetical, subjective statement about his own perspective of the world. Then, greenrd brings in the well–known distinction between psychology and logic. This was often used by Russell to relegate his opponents to the class of subjective, introspective psychologists, while he triumphantly stood on the firm ground of universally objective logic.Lestrade 15:48, 27 September 2007 (UTC)Lestrade
- Sure, i agree, in my understanding identity of indiscernibles is a metaphysical principal rather then epistemological one, but if someone find sites of famous philosophers thinking otherwise, the article should reflect it. --Hq3473 03:46, 15 February 2007 (UTC)
[edit] Critique
Max Black has argued against the identity of indiscernibles by counterexample. Notice that to show that 2. is false, it is sufficient that one provide a model in which there are two distinct (non-identical) things that have all the same properties. He claimed that in the symmetric universe where only two symmetrical spheres exist, the two spheres are two distinct objects, even though they have all the properties in common.
I know that Max Black is correct because I am in possession of a wonderful counterexample from pure mathematics--in other words, I have an elegant simple model--which proves, conclusively and persuasively, that there is at least one pair of numerically distinct objects which--nevertheless--have all their properties in common. And as soon as I have my proof published, or submitted, to a scholarly peer-reviewed philosophical journal, I look forward of the opportunity of publishing it here in this excellent Wikipedia article. Ludvikus
03:50, 2 September 2006 (UTC)
I've transcribed here the above from the Article page - before reversion. I have written the
comment before having become an experienced Wikipedian, understanding and following WP policy.
Nevertheless, my observation remains true. But like Fermat? - No space to ellaborate?
Yours truly,--Ludvikus 03:22, 14 December 2006 (UTC)
I would say that Mr. Black's critique doesn't hold water, as the two spheres he describes obviously occupy different locations in space. As location in space counts as a property, then the two spheres do not have the same properties. Anyone disagree? -Tim —Preceding unsigned comment added by 218.219.191.130 (talk) 00:07, 10 September 2007 (UTC)
- Yeah, there is no such thing as "space", the only way to define space is in relation to other objects. So in the world with only 2 objects the only space for a spehere is defined by "distance to the other sphere" but the ther sphere will have the same prperty, so we still cannot distinguish them. See Theory of relativity.--Hq3473 02:09, 10 September 2007 (UTC)
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- Ok, it took me a bit of thinking to figure out what seemed wrong about your response, and here it is: First, Black says that the only two things that exist in this hypothetical universe are the two spheres. This, however, cannot be technically accurate, as the properties that we are using to describe those spheres must also exist. So what properties exist? Obviously, numerical, spatial, and physical ones exist, as the spheres exist in space and have size, shape and numerosity. Of course, their size and shape are the same. However, logical properties must also exist. And the critical flaw in Black's example is that with the very act of saying that two spheres exist, he imbues them with the logical property of not being the same object. Sphere A is sphere A. Sphere B is sphere B. Sphere A is not sphere B, and vice-versa. What made me realize this was your response to me in which you wrote "distance to the OTHER sphere." In order for "other" to have any meaning, there would have to be some property that differed between the spheres that allowed us to tell them apart - and that property was the logical one that they have been defined as two separate objects from the start. Any objections to that? - Tim —Preceding unsigned comment added by 125.201.152.222 (talk) 11:48, 14 September 2007 (UTC)
- No by saying there are two sphere Black does NOT give you the power to differentiate spheres. Sure if a spectator were to appear in the Black's world he would immediately identify spheres as 1 and 2. But there is no spectator. Think about it this way. Say you pick a sphere and call it Spehere 1 and the other one Spehere 2. Then you leave the world, and then come back again. WOuld you be able to tell which one is Sphere 1 and which one is spehere 2? No you would not. Because Max's world has no way to differentiate the spheres. --Hq3473 13:28, 20 September 2007 (UTC)
- I'm sorry, I think I worded my comment above somewhat badly. What I meant when I wrote "there would have to be some property that differed between the spheres that allowed us to tell them apart" was not that we would be able to tell which sphere was A and which was B (after having labeled them and then re-entered Max's world). You are right; we would not be able to tell.
- No by saying there are two sphere Black does NOT give you the power to differentiate spheres. Sure if a spectator were to appear in the Black's world he would immediately identify spheres as 1 and 2. But there is no spectator. Think about it this way. Say you pick a sphere and call it Spehere 1 and the other one Spehere 2. Then you leave the world, and then come back again. WOuld you be able to tell which one is Sphere 1 and which one is spehere 2? No you would not. Because Max's world has no way to differentiate the spheres. --Hq3473 13:28, 20 September 2007 (UTC)
- Ok, it took me a bit of thinking to figure out what seemed wrong about your response, and here it is: First, Black says that the only two things that exist in this hypothetical universe are the two spheres. This, however, cannot be technically accurate, as the properties that we are using to describe those spheres must also exist. So what properties exist? Obviously, numerical, spatial, and physical ones exist, as the spheres exist in space and have size, shape and numerosity. Of course, their size and shape are the same. However, logical properties must also exist. And the critical flaw in Black's example is that with the very act of saying that two spheres exist, he imbues them with the logical property of not being the same object. Sphere A is sphere A. Sphere B is sphere B. Sphere A is not sphere B, and vice-versa. What made me realize this was your response to me in which you wrote "distance to the OTHER sphere." In order for "other" to have any meaning, there would have to be some property that differed between the spheres that allowed us to tell them apart - and that property was the logical one that they have been defined as two separate objects from the start. Any objections to that? - Tim —Preceding unsigned comment added by 125.201.152.222 (talk) 11:48, 14 September 2007 (UTC)
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- Let me put my argument in other words: If more than one object exists in a universe, then those objects will always be identifiable as different by means of logical properties. This is why: We know from Max's definition of his world that the Sphere A and Sphere B are separate objects. If so, then Sphere A logically *must* have the property of being "not equal to Sphere B." Likewise, Sphere B must have the property of being "not equal to Sphere A." Without these properties, we would be literally unable to conceive of Spheres A and B as being two separate objects; we would have to conclude that "Sphere A" and "Sphere B" were simply two different names for the exact same thing. In case you aren't convinced, take the example of an object lacking, say, a certain mathematical property. Let us say that this object has no numerosity. It is not a single object, nor is it many; the idea of numerosity simply does not apply. Can you imagine it? I can't. I can imagine one object and I can imagine more than one, but no matter how I try, I cannot conceive of an object without numerosity. (Nor can I talk about it! Notice how I had to use singular pronouns and verb conjugations to describe the object.) Sphere A and Sphere B are in the same boat, with reference to logical properties. We cannot conceive of their being separate objects unless each has the property of being not equal to the other.
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- Logical properties are so taken-for-granted that they are easy to forget. Think of a person debating whether the Law of Noncontradiction is true, not realizing that they are assuming it's true in order to have the debate. Max Black must have forgotten about logical properties, or not thoroughly understood them, when he made his argument against the law of indiscernibles.
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- One last thing I could say, although this argument shouldn't be necessary given the above, is that Sphere A and Sphere B *do* have different properties as per their location, despite what Hq3473 wrote before. Consider that Sphere A has the property of being 0 distance from Sphere A, while Sphere B has the property of being some non-zero distance from Sphere A. There's something else they don't have in common. -Tim
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- You seem to have begged the question at "Sphere A logically *must* have the property of being "not equal to Sphere B." Such thing does not follow from "Sphere A and Sphere B are separate objects." This is the whole argument that Max is trying to make -- A and B are separate objects yet Sphere A does NOT has a property of being not equal to B, in fact it IS equal to B. This is the whole point --to show that by using identity of indiscernibles we get two separate object which are nevertheless equal, and to straight up assume otherwise amounts to saying "A and B are not equal because they are not equal." In the end Max's attack works, because either you have to accept that Spheres are "separate but equal" or you eviscerate the Identity of indiscernibles by saying that all distinct objects have the property of being different from other objects and thus are different from other objects. How would such law be useful?--Hq3473 15:23, 27 September 2007 (UTC).
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- I agree with the grandparent, the argument doesn't hold water. Max Black must construct a space in which to embed to objects, even if this is the topological/geometric/set/etc. construct of "just two spheres." However, if we were to refer to just the simple constructivist approach of S={A,B}, where A,B are elements of the set "Sphere" then we can ask what properties they have in common (up to the Leibniz equality). However, Max Black is implicitly adding more properties: symmetry and an embedding in "the universe". Now, the description in Wikipedia is too weak to make any meaningful conjecture, but knowing the sort of reasoning logicians/philosopher's use, he's probably thinking of a closed, bounded, infinite symmetric space like unit cell of P2; see Crystallography. In that case, while P2 does not discern handedness, orientation, etc., it still provides an infinite number of exactly equivalent metric embeddings. In any of these embeddings we can determine the vector offset (for free, with no additional assumptions), uniquely between the two pairs. If you assume that no meaningful embedding occurs, then you must add in the assumption to the set construction that A does not equal B, and thus, Max Black (and the parent) are begging the question. —Preceding unsigned comment added by 128.194.143.200 (talk) 16:54, 4 March 2008 (UTC)
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[edit] Epistemological Version
The articles gives the above rather than an ontological principle:
The identity of indiscernibles is an ontological principle that states that if there is no way of telling two entities apart then they are one and the same entity. That is, entities x and y are identical if and only if any predicate possessed by x is also possessed by y and vice versa.
- Yours truly,--Ludvikus 03:53, 14 December 2006 (UTC)
[edit] Ontological principle
I've modified/corrected the opening sentence from the above, to the following:
The identity of indiscernibles is an ontological principle; i.e., that if (two
or more) object(s), or entity/ies have all thier/its property/ies in
common then they (it) are identical (are one and the same entity). That is, entities x and
y are identical if and only if any predicate possessed by x is also possessed by y and
vice versa.
- Yours truly,--Ludvikus 04:05, 14 December 2006 (UTC)
So you're the one I should kick in the balls for making it needlessly illegible. Great. I'll change it back to English now. --76.224.107.34 20:36, 10 June 2007 (UTC)
[edit] Criticism Counterexample
The proposed criticism is: "Opponents of this counterexample would claim that a contradiction can be found between proposition (2) and (3) (i.e. Lois Lane cannot have opposite thoughts about the same object, regardless of the name)." To me this objection seems like begging the question. Lane think that the person can and can't fly at the same time because she does not know that it is the same person. So she DOES have opposite thoughts, and denying it begs the question: I.E. it is arguing for "Identity of indiscernibles" like this: "I know that Identity of indiscernibles is true, and therefore your counterexample(no matter what it is) cannot work". Thus i propose deleting this weak objection. --Hq3473 23:24, 1 March 2007 (UTC)
[edit] Quine's Variation
The most well spoken version of the identification of indiscernibles I have encountered is found in Quine's "Identity, Ostension, and Hypostasis," as follows: "Objects indistinguishable from one another within the terms of a given discourse should be construed as identical for that discourse." This gets us away from descriptions about properties and the like, which of course invite the confusion of supposing that the creation of two objects with identical sets of properties might disprove the proposition (Liebniz would argue that, for this to be the case, you would have to find a way to have two identical objects occupying the same spatio-temporal location as well, which makes a refutation of this kind rather hard to manage, unless you can imagine two individual objects occupying the same space), or suggesting that a single object, seen, say, from two different perspectives, would also disprove the proposition. Of course, the Quinean version is not ontological in the sense of defining specificity to real objects in the physical universe. It is a deliberately broad definition, intended to deal with another set of representational philosophical problems that are only partly related to what Liebniz was interested in demonstrating. Nevertheless, it would seem to me a worthy candidate for admission in this article, for some plucky chap willing to add it in.
- Feel free to write about Quine's version, its advantages and shortcomings, etc. Make sure to source to Quine.--Hq3473 03:46, 19 April 2007 (UTC)
[edit] Descartes' argument
I don't think that Descartes' argument should be described as an application of the identity of indiscernables. Note that the conclusion, that the body and the mind are different, states that two things are not identical. If anything, this would be an instance of principle 1, the indiscernibility of identicals. Zarquon 03:48, 19 April 2007 (UTC)
- The definition in the first paragraph says: "The identity of indiscernibles is an ontological principle: that if and only if. Not that the "if and only if" part makes the Identity of indiscernibles work both ways. --Hq3473 04:59, 19 April 2007 (UTC)
[edit] "Controversial Applications" not true
Entities x and y are identical if and only if any predicate possessed by x is also possessed by y and vice versa. Clark Kent is Superman's secret identity; that is, they're the same person (identical) but people don't know this fact. Lois Lane thinks that Clark Kent cannot fly. Lois Lane thinks that Superman can fly. Therefore Superman has a property that Clark Kent does not have, namely that Lois Lane thinks that he can fly. Therefore, Superman is not identical to Clark Kent. Since in proposition 6 we come to a contradiction with proposition 2, we conclude that at least one of the premises is wrong. Either: Leibniz's law is wrong; or else A person's knowledge about x is not a predicate of x, thus undermining Descartes' argument.
The conclusion "Since in proposition 6 we come to a contradiction with proposition 2, we conclude that at least one of the premises is wrong." has been obtained ridiculously. To show that this is an invalid argument, firstly we consider the statement "Therefore Superman has a property that Clark Kent does not have, namely that Lois Lane thinks that he can fly.". Simply put a property of an object must be inherent to itself and not based on some observers view. It is also possible that we cannot confirm that an object has a certain property or not, in which case be contradictory by saying that an electron is a wave and not a particle or vice versa, then when observed we "think" it is a wave or particle, thus appearing contradictory based on the identity of indiscernibles. In that case we cannot say whether the electron is identical to itself and cannot make any conclusions.
Nicholaslyz 10:30, 9 July 2007 (UTC)
- Note that you say that " Simply put a property of an object must be inherent to itself and not based on some observers view", this is the point of the "proof" precisely. Descartes tried to rely on a human belief about an object as a property of an object, this exact line of reasoning the "proof" aims to debunk.--Hq3473 20:24, 9 July 2007 (UTC)
[edit] Contradictory and incorrect(?) definitions; Proposed article split
The lead defines identity of indiscernables as being: two objects are equal if and only if they have all properties in common. However, further down, identity of indiscernables is distinguished from indiscernability of identicals: the two halves of the if-and-only-if. But it can't be half of itself...
Moreover, many authors use Leibniz's Law to mean only indiscernability of identicals, and the first comment on this very talk page says that identity of indiscernables is not one of Leibniz's great metaphysical principles, although he accepted it.
I think it would make sense to split this page into two separate articles: identity of indiscernables and indiscernability of identicals. I mean, Black's objection is directed at the identity of indiscernables, and the Superman confusion relates to the indiscernability of identicals. Vaccillation between covering the two principles makes for a confusing article.
Let me ask the question: Is there any evidence that any reliable source apart from Wikipedia has treated these two principles together - or that the value of doing so outweighs any confusion created?—greenrd 01:45, 27 October 2007 (UTC)
- Oppose split. The introduction can be altered from "if and only if" to the correct statement. I can see where the confusion lies in the Superman example. As for splitting it, I think it would be better to just rename the article to something more appropriate, and have a distinct separation within the article itself. Necessary and sufficient accomplishes this. — metaprimer (talk) 13:18, 27 October 2007 (UTC)
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- First, thanks for removing the self-contradiction. I think there is an important difference between this article and necessary and sufficient - this article could probably benefit from more expansion (e.g. where they have been applied to try and prove various statements, other controversies about them, etc.); and if it is likely to become a long article containing two sub-articles without much overlap between them (and with potential for confusion!) it makes sense to split it up into two articles.
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- My point about the Superman section - which I didn't make very clearly, I admit - was that both Descartes' argument and the Superman "paradox" are applications of the indiscernibility of identicals (contrary to what the section currently says).
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- Also, what would be a good new name, if we kept this article as one article? "Identity of indiscernibles and indiscernibility of identicals" is too long and awkward, in my opinion.—greenrd 13:42, 27 October 2007 (UTC)
[edit] Response to Black's critique
Is there a reference for this "response", or is it original research?--Hq3473 22:50, 28 October 2007 (UTC)
- It's original research. I'm aware of WP:NOR, but I added it in the hope that no-one would object, in the spirit of WP:IAR. Feel free to remove it.—greenrd 08:19, 29 October 2007 (UTC)
- I will remove, because it addition to being OR it does not seem a particularly strong response to Max Black. Sure the universe can be looped, but this just goes to show that Identity of indiscernibles will lead to weird counter-intuitive results. --Hq3473 13:26, 29 October 2007 (UTC)
[edit] Secret identity.
The example in the article concludes;
- Leibniz's law is wrong; or else
- A person's knowledge about x is not a predicate of x, thus undermining Descartes' argument.
However it seems to me that it might just as well be the claim that superman is equal to clark kent that is wrong. Ie. the claim that they are the same person is weaker than the claim that they are equal.
An example that does not involve other peoples believes would be the Supreme Governor of the Church of England and the Paramount Chief of Fiji. The first having the right to formally appoint high-ranking members of the church of England. Taemyr (talk) 17:56, 6 April 2008 (UTC)
[edit] The Principle "states that two or more objects...are identical..."?!
Surely the principle doesn't state, as the article now says it does, that "two or more objects or entities are identical if...." If it really does state that, then it's clearly absurd; for how can two objects be identical? Isokrates (talk) 20:56, 19 April 2008 (UTC)
- It is usual in formal arguments to interpret "two objects" as "two objects that might be instances of the same object." When you require them to be two seperate object this usually needs to be stated. So a relation ≤, is antisymmetric if for any two objects a≤b and b≤a implies a=b. Compare to ... for any two objects a≤b and b≤a is a contradiction. Taemyr (talk) 19:36, 20 April 2008 (UTC)
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- Your example is not as helpful as it appears. Every two objects are instances of a<b. And every one object is an instance of a=a. No object(s) is/are instances of both. --Ludvikus (talk) 21:22, 20 April 2008 (UTC)
- I'm saying that you really cannot instantiate the relation you give above - although you do conform by it to standard practice (it's as if 2 contradictions are wiping each other out). --Ludvikus (talk) 21:30, 20 April 2008 (UTC)
- What a strange relation: "something is greater than or equal to something
else"! --Ludvikus (talk) 21:32, 20 April 2008 (UTC)
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- I should perhaps not have used the symbol ≤. Remember that we are defining our relation. So don't pressupose arithmetic "less than or equal", arithmetic "less than or equal" is simply an instance of an antisymetric relation. And no, every two objects need not be instances of where a and b is different. You usually has to specify it explicitly when you want to say that you are reasoning about pairs of un-equal elements. Taemyr (talk) 07:28, 21 April 2008 (UTC)
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[edit] Two objects are one if such and such is the case.
I just want to simplify that ordinary language version of the alleged apparent self-contradiction. --Ludvikus (talk) 21:16, 20 April 2008 (UTC)
- How about Hepsherus and Phosporus both being Venus? Hesperus#"Hesperus is Phosphorus".--Hq3473 (talk) 01:08, 21 April 2008 (UTC)
- "Two objects are one", I think this is the heart of the reason why the above poster sees a contradiction. His view is that two objects are never one. So getting around the percieved contradiction while retaining formal correctness would require something like "Two differing objects never share every property." Taemyr (talk) 07:33, 21 April 2008 (UTC)
- I personally like the definition from Quine given earlier on this talk page. "Objects indistinguishable from one another within the terms of a given discourse should be construed as identical for that discourse." Because this definition includes which properties are of intererest or not. Taemyr (talk) 07:39, 21 April 2008 (UTC)

