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9. Objects / F. Identity among Objects / 9. Sameness

[how we should understand two things being 'the same']

9 ideas
'Same' is mainly for names or definitions, but also for propria, and for accidents [Aristotle]
     Full Idea: 'The same' is employed in several senses: its principal sense is for same name or same definition; a second sense occurs when sameness is applied to a property [idiu]; a third sense is applied to an accident.
     From: Aristotle (Topics [c.331 BCE], 103a24-33)
     A reaction: [compressed] 'Property' is better translated as 'proprium' - a property unique to a particular thing, but not essential - see Idea 12262. Things are made up of essence, propria and accidents, and three ways of being 'the same' are the result.
Two identical things have the same accidents, they are the same; if the accidents differ, they're different [Aristotle]
     Full Idea: If two things are the same then any accident of one must also be an accident of the other, and, if one of them is an accident of something else, so must the other be also. For, if there is any discrepancy on these points, obviously they are not the same.
     From: Aristotle (Topics [c.331 BCE], 152a36)
     A reaction: So what is always called 'Leibniz's Law' should actually be 'Aristotle's Law'! I can't see anything missing from the Aristotle version, but then, since most people think it is pretty obvious, you would expect the great stater of the obvious to get it.
Numerical sameness and generic sameness are not the same [Aristotle]
     Full Idea: Things which are the same specifically or generically are not necessarily the same or cannot possibly be the same numerically.
     From: Aristotle (Topics [c.331 BCE], 152b32)
     A reaction: See also Idea 12266. This looks to me to be a pretty precise anticipation of Peirce's type/token distinction, but without the terminology. It is reassuring that Aristotle spotted it, as that makes it more likely to be a genuine distinction.
Things are the same if one can be substituted for the other without loss of truth [Leibniz]
     Full Idea: Leibniz's definition is as follows: Things are the same as each other, of which one can be substituted for the other without loss of truth ('salva veritate').
     From: Gottfried Leibniz (works [1690]), quoted by Gottlob Frege - Grundlagen der Arithmetik (Foundations) §65
     A reaction: Frege doesn't give a reference. (Anyone know it?). This famous definition is impressive, but has problems when the items being substituted appear in contexts of belief. 'Oedipus believes Jocasta (his mother!) would make a good wife'.
A tree remains the same in the popular sense, but not in the strict philosophical sense [Butler]
     Full Idea: When a man swears to the same tree having stood for fifty years in the same place, he means ...not that the tree has been all that time the same in the strict philosophical sense of the word. ...In a loose and popular sense they are said to be the same.
     From: Joseph Butler (Analogy of Religion [1736], App.1)
     A reaction: A helpful distinction which we should hang on. Of course, by the standards of modern physics, nothing is strictly the same from one Planck time to the next. All is flux. So we either drop the word 'same' (for objects) or relax a bit.
There is 'loose' identity between things if their properties, or truths about them, might differ [Chisholm]
     Full Idea: I suggest that there is a 'loose' sense of identity that is consistent with saying 'A has a property that B does not have', or 'some things are true of A but not of B'.
     From: Roderick Chisholm (Person and Object [1976], 3.2)
     A reaction: He is trying to explicate Bishop Butler's famous distinction between 'strict and philosophical' and 'loose and popular' senses. We might want to claim that the genuine identity relation is the 'loose' one (pace the logicians and mathematicians).
Being 'the same' is meaningless, unless we specify 'the same X' [Geach]
     Full Idea: "The same" is a fragmentary expression, and has no significance unless we say or mean "the same X", where X represents a general term. ...There is no such thing as being just 'the same'.
     From: Peter Geach (Mental Acts: their content and their objects [1957], §16)
     A reaction: Geach seems oddly unaware of the perfect identity of Hespherus with Phosphorus. His critics don't spot that he was concerned with identity over time (of 'the same man', who ages). Perry's critique emphasises the type/token distinction.
A vague identity may seem intransitive, and we might want to talk of 'counterparts' [Kripke]
     Full Idea: When the identity relation is vague, it may seem intransitive; a claim of apparent identity may yield an apparent non-identity. Some sort of 'counterpart' notion may have some utility here.
     From: Saul A. Kripke (Naming and Necessity notes and addenda [1972], note 18)
     A reaction: He firmly rejects the full Lewis apparatus of counterparts. The idea would be that a river at different times had counterpart relations, not strict identity. I like the word 'same' for this situation. Most worldly 'identity' is intransitive.
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.