display all the ideas for this combination of texts
6 ideas
| 16497 | Leibniz's Law (not transitivity, symmetry, reflexivity) marks what is peculiar to identity [Wiggins] |
| Full Idea: The principle of Leibniz's Law marks off what is peculiar to identity and differentiates it in a way in which transitivity, symmetry and reflexivity (all shared by 'exact similarity, 'equality in pay', etc.) do not. | |
| From: David Wiggins (Sameness and Substance [1980], 1.2) |
| 16502 | Identity is primitive [Wiggins] |
| Full Idea: Identity is a primitive notion. | |
| From: David Wiggins (Sameness and Substance [1980], 2.1) | |
| A reaction: To be a true primitive it would have to be univocal, but it seems to me that 'identity' comes in degrees. The primitive concept is the minimal end of the degrees, but there are also more substantial notions of identity. |
| 16498 | Identity cannot be defined, because definitions are identities [Wiggins] |
| Full Idea: Since any definition is an identity, identity itself cannot be defined. | |
| From: David Wiggins (Sameness and Substance [1980], 1.2 n7) | |
| A reaction: This sounds too good to be true! I can't think of an objection, so, okay, identity cannot possibly be defined. We can give synonyms for it, I suppose. [Wrong, says Rumfitt! Definitions can also be equivalences!] |
| 16521 | A is necessarily A, so if B is A, then B is also necessarily A [Wiggins] |
| Full Idea: The famous proof of Barcan Marcus about necessity of identity comes down to simply this: Hesperus is necessarily Hesperus, so if Phosphorus is Hesperus, Phosphorus is necessarily Hesperus. | |
| From: David Wiggins (Sameness and Substance [1980], 4.3) | |
| A reaction: Since the identity of Hesperus and Phosphorus was an a posteriori discovery, this was taken to be the inception of the idea that there are a posteriori necessities. The conclusion seems obvious. One thing is necessarily one thing. |
| 16505 | By the principle of Indiscernibility, a symmetrical object could only be half of itself! [Wiggins] |
| Full Idea: The full Identity of Indiscernibles excludes the existence in this world of a symmetrical object, which is reduced to half of itself by the principle. If symmetrical about all planes that bisect it, it is precluded altogether from existence. | |
| From: David Wiggins (Sameness and Substance [1980], 2.2) | |
| A reaction: A really nice objection. Do the parts even need to be symmetrical? My eyeballs can't be identical to one another, presumably. Electrons already gave the principle big trouble. |
| 16494 | We want to explain sameness as coincidence of substance, not as anything qualitative [Wiggins] |
| Full Idea: The notion of sameness or identity that we are to elucidate is not that of any degree of qualitative similarity but of coincidence as a substance - a notion as primitive as predication. | |
| From: David Wiggins (Sameness and Substance [1980], Pre 2) | |
| A reaction: This question invites an approach to identity through our descriptions of it, rather than to the thing itself. There is no problem in ontology of two substances being 'the same', because they are just one substance. |