Abstract

My dissertation evaluates Peter Geach's theory of relative identity. Typically discussions of relative identity focus on predicative identity expressions of the form "is the same A as". My approach, following Geach, is broader: it also looks at how, if correct, the theory of relative identity must play into our accounts of proper names and quantifiers. ;Geach's theory is well known for denying the coherence of the concept of absolute identity, and for its espousal of a concept of identity allowing true instances of "a is the same A as b and not -F and F". This position requires a positive theory of identity which does not covertly rely upon a Leibnizian understanding of identity to account for substitution, and does not covertly rely upon absolute identity to explain reference . I do not evaluate Geach's denial of absolute identity, but rather evaluate the positive theory of relative identity. ;To enable us to see more clearly what is involved in Geach's theory, I define several language structures which transparently embody aspects of the theory. I examine a series of examples in which one may be inclined to accept descriptions which require a non-Leibnizian understanding of the description's identity expressions. I then look at how the notion of individuating identity plays into truth conditions for ordinary predications of the form "F"; we consider what support this gives to Geach's view that proper names convey identity criteria as part of their sense. I address problems arising from temporal aspects of Geach's account of reference. Quantification is explained recursively in terms of sentences involving proper names. I consider consequences of Geach's views regarding what must be counted as a valid argument . A non-Leibnizian account of substitution is offered. Wiggins's thesis R is discussed