What is what

A.J. Ayer

  • Sameness and Substance by David Wiggins
    Blackwell, 238 pp, £12.50, May 1980, ISBN 0 631 19090 2

Professor Wiggins’s new book was originally intended to be a revision of his book Identity and Spatio-Temporal Continuity, which appeared in 1967 and had been allowed to go out of print. Like the earlier book, it is concerned with questions of identity, and especially with the identity of things which persist through change, and it advances the same theory of individuation. So much, however, has been added, and so earnest an attempt has been made to clarify what the earlier book had left obscure, that this ranks as an independent work. Though it is less arcane than its predecessor, the density of its argument and the author’s predilection for symbols still make it difficult reading, but the philosophical interest of its subject, and the thorough honesty of its treatment, more than make up for this deficiency. There is no denying the importance of having a proper theory of identity, and even if not all his arguments carry equal conviction, the attempt which Wiggins has made to supply this need deserves to be treated with very great respect.

The identity with which Wiggins is concerned is primarily that of concrete individuals and is therefore encompassed in his theory of individuation. The demand which he makes of a theory of individuation is that it ‘comprise at least three things: first, an elucidation of the primitive concept of identity as sameness; second, some however abstract account of what it is for something to be a substance that persists through change; and third, (supervening in [his] treatment upon the first two things) the beginnings of some lifelike description, however schematic, of what it is for a thinker at one time and then another to single out the same substance as the same substance’. Wiggins’s way of meeting these demands is to engage in what Strawson once called descriptive metaphysics. He sees himself as bringing to light the principles that govern our use of a crucial set of terms, thereby at once illuminating the structure of our thought and the character of a central part of its subject matter.

As in his earlier book, Wiggins takes his stand upon ‘Leibniz’s Law’, which states that if a is the same as b, what is true of a is true of b and vice versa. This principle, which is sometimes known as the Indiscernibility of Identicals, is professed by Wiggins, not as a definition of identity, which he takes to be a primitive notion, but as part of the elucidation of its nature. He also maintains that if a and b are identical, there must be some sortal concept f which assigns both a and b to some natural or artificial kind and accounts for the manner of their coincidence. Thus, on this view, a cannot simply be the same as b: it has to be the same something as b and the character of this something, whether it be a mountain or a motor-car or a donkey or a person, determines how the identity of a or b is constituted in the case in question.

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