- In "Lewis (David) - On the Plurality of Worlds" (pp. 192-3), David Lewis says:
Identity is utterly simple and unproblematic. Everything is identical to itself; nothing is ever identical to anything else except itself. There is never any problem about what makes something identical to itself; nothing can ever fail to be. And there is never any problem about what makes two things identical; two things never can be identical.
- One can readily agree that identity is a simple1, obvious relation. But then why do we have various identity puzzles such as puzzles about mind-body identity, personal identity, and the identity of material objects through time? Some of us claim that the identity of things depends on time or the world in which they are located, and that there are temporary or contingent identities. Some also claim that identity is not such a clear-cut matter because it is sometimes indeterminate whether a is identical to b; in other words, identities are sometimes vague. Is identity not really as simple a relation as Lewis claims it to be?
- Indeed it is a simple relation, and the main task of this paper is to show that those who think otherwise are confused. There are at least two ways in which identity is mistakenly considered to be a substantial and problematic subject: first, identity is considered to be the main issue when in fact something else is; second, people tend to speak of identity when they are actually dealing with something else, in particular, mere coincidence. In the next few pages, then, we shall encounter various examples of these two kinds, although much more of the second than the first. The discussion will reveal that even if an object has some puzzling features, for instance, even if it has (spaciously, temporally, or modally)2 indeterminate borderlines, that does not affect the simplicity of its identity, and this claim is not refuted by the various arguments that have been made against it, such as "Evans (Gareth) - Can There Be Vague Objects?" (1978). At the end of this essay, we shall confront critically Kripke's argument in "Kripke (Saul) - Naming and Necessity" against the mind-body identity theory. Although Kripke has contributed more than anybody else to the clarification of the issues surrounding identity, he has failed to see some subtler points, and a major revision is necessary for his theory to take them into account. Or so it is argued.
- Some of the materials presented here (especially those in Section III) are already familiar to many. But the reader will see those familiar bits and pieces integrated into a unified picture concerning identity; in particular, the unification of the issues about temporal3 and contingent identity4 (Section III) and vague identity5 (Sections IV and V) will be of great significance. My hope is that the reader can obtain from this article a better overall view of the issues surrounding identity and related notions.
- Identity Puzzles
- Temporary6 and Contingent Identity7
- Vague Identity
- Indeterminacy in Sentence and Proposition
- Against Kripke
Footnote 3: This appears to be what is usually called Occasional Identity.
- Does Akiba therefore adopt the Simple View, as his title might suggest?
- That said, the Simple View is a position on Personal Identity – claiming that PID is not reducible to anything else – rather than a position on the logic of identity itself.
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