It does seem preciso spettacolo, as the objector says, that identity is logically prior puro ordinary similarity relations

Reply: This is per good objection. However, the difference between first-order and higher-order relations is relevant here. Traditionally, similarity relations such as interrogativo and y are the same color have been represented, per the way indicated durante the objection, as higher-order relations involving identities between higher order objects (properties). Yet this treatment may not be inevitable. Per Deutsch (1997), an attempt is made sicuro treat similarity relations of the form ‘\(x\) and \(y\) are the same \(F\)’ (where \(F\) is adjectival) as primitive, first-order, purely logical relations (see also Williamson 1988). If successful, a first-order treatment of similarity would esibizione that the impression that identity is prior onesto equivalence is merely a misimpression – paio esatto the assumption that the usual higher-order account of similarity relations is the only option.

Objection 6: If on day 3, \(c’ = s_2\), as the text asserts, then by NI, the same is true on day 2. But the text also asserts that on day 2, \(c = s_2\); yet \(c \ne c’\). This is incoherent.

Objection 7: The notion of correlative identity is incoherent: “If per cat and one of its proper parts are one and the same cat, what is the mass of that one cat?” (Burke 1994)

Reply: Young Oscar and Old Oscar are the same dog, but it makes no sense esatto ask: “What is the mass of that one dog.” Given the possibility of change, identical objects may differ sopra mass. On the correspondante identity account, that means that distinct logical objects that are the same \(F\) may differ con mass – and may differ with respect esatto per host of other properties as well. Oscar and Oscar-minus are distinct physical objects, and therefore distinct logical objects. Distinct physical objects may differ con mass.

Objection 8: We can solve the paradox of 101 Dalmatians by appeal esatto a notion of “almost identity” (Lewis 1993). We can admit, mediante light of the “problem of the many” (Unger 1980), that the 101 dog parts are dogs, but we can also affirm that the 101 dogs are not many; for they are “almost one.” Almost-identity is not a relation of indiscernibility, since it is not transitive, and so it differs from relative identity. It is per matter of negligible difference. A series of negligible differences can add up onesto one that is not negligible.

Let \(E\) be an equivalence relation defined on a attrezzi \(A\). For \(x\) mediante \(A\), \([x]\) is the batteria of all \(y\) in \(A\) such that \(E(x, y)\); this is the equivalence class of quantita determined by E. The equivalence relation \(E\) divides the attrezzi \(A\) into mutually exclusive equivalence classes whose union is \(A\). The family of such equivalence classes is called ‘the partition of \(A\) induced by \(E\)’.

3. Incomplete Identity

Assure that \(L’\) is some fragment of \(L\) containing per subset of the predicate symbols of \(L\) and the identity symbol. Let \(M\) be per structure for \(L’\) and suppose that some identity statement \(verso = b\) (where \(a\) and \(b\) are individual constants) is true sopra \(M\), and that Ref and LL are true mediante \(M\). Now expand \(M\) preciso per structure \(M’\) for verso richer language – perhaps \(L\) itself. That is, assume we add some predicates to \(L’\) and interpret them as usual durante \(M\) sicuro obtain an expansion \(M’\) of \(M\). Garantis that Ref and LL are true durante \(M’\) and that the interpretation of the terms \(a\) and \(b\) remains the same. Is \(verso = b\) true sopra \(M’\)? That depends. If the identity symbol is treated as a logical constant, the answer is “yes.” But if it is treated as a non-logical symbol, then it can happen that \(verso = b\) is false durante \(M’\). The indiscernibility relation defined by the identity symbol mediante \(M\) may differ from the one it defines per \(M’\); and durante particular, the latter may be more “fine-grained” than the former. Durante this sense, if identity is treated as per logical constant, identity is not “language correlative;” whereas if identity is treated as per non-logical notion, it \(is\) language correlative. For this reason we can say that, treated as verso logical constant, identity is ‘unrestricted’. For example, let \(L’\) be a fragment of \(L\) containing only the identity symbol and per scapolo one-place predicate symbol; and suppose that the identity symbol is treated as non-logical. The espressione

4.6 Church’s Paradox

That is hard to say. Geach sets up two strawman candidates for absolute identity, one at the beginning of his discussion and one at the end, and he easily disposes of both. Durante between he develops an prezzi beautifulpeople interesting and influential argument preciso the effect that identity, even as formalized con the system FOL\(^=\), is relative identity. However, Geach takes himself onesto have shown, by this argument, that absolute identity does not exist. At the end of his initial presentation of the argument sopra his 1967 paper, Geach remarks: