Talk:Law of identity
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feel free to delete this line, but i think someone should know that quote literally gave me a seizure... Longcheeseconey (talk) 05:53, 2 January 2008 (UTC)
Apparently Wundt credits Leibniz with the symbolic formulation, "A is A":
Wundt dit que "la loi d'identité a été exprimée pour la première fois sous une forme logique pure par Leibniz (Logik, t. II, p. 562)". De fait, celui-ci en a proposé un grand nombre de formules, parmi lesquelles : "Chaque chose est ce qu'elle est", "A est A, B est B" (Nouveaux Essais sur l'Entendement humain, IV, 2, éd. Gehrardt, p. 343, sq.). (http://perso.orange.fr/thomiste/eternelb.htm)
I am not sure why this is called a 'tautology' (it might just be one in ordinary language, but not in logic) since it cannot be expressed as such via the truth tables.
http://homepage.ntlworld.com/rosa.l/
Rosa Lichtenstein 14:11, 24 December 2006 (UTC)
I agree A is A (A=A) is not a TAUTOLOGY because A would be a TERM not a STATEMENT. Terms are neither true nor false, so we could not have a tuth table for A=A, or is(A,A). Perhaps the original author meant that A is A (A=A) is a LOGICAL TRUTH (is necessarily true) and of course not all logical truths are tautologies. Because A in A+A is term not a proposition it follows you cannot have a truth table for it.--Philogo 19:42, 29 July 2007 (UTC)
Once more, why is this called a 'tautology'. It isn't one in logic, even if it might be called one colloquially.
And what is the number one doing here:
In philosophy, the law is often attributed to Aristotle, although it is also claimed that Aristotle never gave this law1.
There is no footnote 1!
And the quotation takes this 'law' out of context, for not only does Aristotle not mention 'identity', he specifically talks about predication (and since identity is a relation, he cannnot be talking about identity):
"Let us state what, i.e. what kind of thing, substance should be said to be, taking once more another starting-point; for perhaps from this we shall get a clear view also of that substance which exists apart from sensible substances. Since, then, substance is a principle and a cause, let us pursue it from this starting-point. The 'why' is always sought in this form--'why does one thing attach to some other?' For to inquire why the musical man is a musical man, is either to inquire -- as we have said why the man is musical, or it is something else. Now 'why a thing is itself' is a meaningless inquiry (for (to give meaning to the question 'why') the fact or the existence of the thing must already be evident -- e.g. that the moon is eclipsed -- but the fact that a thing is itself is the single reason and the single cause to be given in answer to all such questions as why the man is man, or the musician musical', unless one were to answer 'because each thing is inseparable from itself, and its being one just meant this'; this, however, is common to all things and is a short and easy way with the question). But we can inquire why man is an animal of such and such a nature. This, then, is plain, that we are not inquiring why he who is a man is a man. We are inquiring, then, why something is predicable of something (that it is predicable must be clear; for if not, the inquiry is an inquiry into nothing). E.g. why does it thunder? This is the same as 'why is sound produced in the clouds?' Thus the inquiry is about the predication of one thing of another. And why are these things, i.e. bricks and stones, a house? Plainly we are seeking the cause. And this is the essence (to speak abstractly), which in some cases is the end, e.g. perhaps in the case of a house or a bed, and in some cases is the first mover; for this also is a cause. But while the efficient cause is sought in the case of genesis and destruction, the final cause is sought in the case of being also."
[Bold emphasis added.]
So, I think the article needs amending.
Finally, since this 'law' is foreign to Aristotle, how can the author of this article say:
The law of identity has deep impact on Aristotle's ethics as well. In order for a person to be morally praiseworthy or blameworthy for an action, he or she must be the same person before the act as during the act and after the act. Without the law of identity, Aristotle notes, there can be no responsibility for vice
Personal identity is not the same as the 'law of identity'.
However, I could not find in the Nicomachean Ethics anything like this reference to personal identity; so perhaps the author of this article will provide an exact quotation?
Rosa Lichtenstein 22:39, 21 March 2007 (UTC)
- I removed mention of Nichomachean Ethics. I think it was a hoax. ←BenB4 19:32, 12 September 2007 (UTC)
[edit] Aristotelian Gobbledegook
This article is completely unacceptable. For one thing it misrepresents Aristotle entirely. I don't know what the quoted passage is supposed to prove but it sure is not Aristotle's formulation of the identity principle. All he said was you cannot consistently assert the same thing about the same object in the same way and there is no mention here of that at all. Moreover he did not claim to invent it and no one claims that he invented it. This is simply the first overt mention of it. I'm not working on this article right now so I am not going to give you the ref. All I can say is, if you can't cook, either stay out of the kitchen or learn to cook. So get yourself a nice book on the metaphysics with a nice index telling you where the "first principle" is and settle down to a nice winter of learning metaphysics, which is nice. PS. If this is all we are going to say about the identity principle it probably can be merged with no problem; in fact, if we don't merge there will be a content fork.Dave (talk) 12:31, 17 November 2007 (UTC)
Rather 'unchristian' comments, the above!
Rosa Lichtenstein (talk) 09:46, 2 February 2008 (UTC)
[edit] Locke's law of identity?
I can't find anyone before Locke who ever mentioned a canonical "law of identity". Locke attests it. Leibniz attests it at the same time as Locke. Joseph Butler attests it, a generation after Locke. Before Locke? Nothing. None of the Medieval Scholastics knew anything about it. Aquinas doesn't mention it. William of Ockham doesn't mention it. I've been told that Francisco Suárez attributes something similar to an obscure student of Duns Scotus (Antonius Andreas), but nobody made a big deal out of it at the time, and there was as yet no "law of identity". Interestingly, Descartes mentions no law of identity either, which implies that it was not known as such until 1650-1700. --70.131.116.104 (talk) 21:38, 6 May 2008 (UTC)
