|Identity: Two objects are never identical. Identity is a single object, to which may be referred to with two different terms. The fact that two descriptions mean a single object may be discovered only in the course of an investigation.|
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Identity: Arbitrary criteria (only math required) - not for objects or people
Identity over time: is it still the same object if several parts of a table have been replaced? There is a certain vagueness. Where the identity relation is vague, it might appear intransitive.
A kind of "counterpart" concept could be useful here. (However, without Lewis worlds that are like foreign countries, etc.) You could say that strict identities only apply to individual things (molecules) and the counterpart relation to those individual things that are composed of them, the tables.
Our concept of identity, which we are using here, deals with identity criteria of individual objects in concepts of other individual objects, and not in concepts of qualities.
Identity: Through the use of descriptions one can make contingent identity statements.
Kripke (VsTradition): molecular motion: is necessarily identical with heat. We have discovered it, but it could not be otherwise.
Physical truths necessary: E.g. heat = molecular motion - but no analogy to mind-brain identities.
Ruth Barcan Markus: Thesis: Identities between names are necessary. ("mere tag").
QuineVsMarkus: we could label the planet Venus with the proper name "Hesperus" on a beautiful evening. We could label the same planet again on a day before sunrise, this time with the proper name "Phosphorus". If we discover that it was the same planet twice, our discovery is an empirical one. And not because the proper names have been descriptions.
Designation does not create identity: same epistemic situation, Phospherus/Hesperus named as different celestial bodies - is quite possible, therefore contingent, but does not affect the actual identity - we use them as names in all possible worlds.
Identity: A mathematician writes that x = y are only identical if they are names for the same object. Kripke: Those are not names at all, but rather variables.
Definition "Schmidentity": this artificial relation is only to exist between an object and himself. Kripke: quite okay and useful.
That the mere creation of molecular motion still leaves the additional task for God to turn this motion into heat? This feeling is actually based on an illusion, what God really has to do is to turn this molecular motion into something that is perceived as heat.
Frank I 114
Identity/Kripke: If an identity statement is true, it is always necessarily true. E.g. heat/motion of molecules - Cicero/Tullius - Water/H20 - compatible with the fact that they are truths a posteriori - but according to Leibniz: Not conceivable that one occurs without the other.
Frank I 125
Identity/body/Kripke: "A" is the (rigid) name for the body of Descartes - it survived the body - i.e.: M (Descartes unequal A) - this is not a modal fallacy, because A is rigid - analogue: Statue is dissimilar to molecule collection.
Name und Notwendigkeit Frankfurt 1981
S. A. Kripke
Outline of a Theory of Truth (1975)
Recent Essays on Truth and the Liar Paradox, R. L. Martin (Hg), Oxford/NY 1984
M. Frank (Hrsg.)
Analytische Theorien des Selbstbewusstseins Frankfurt 1994