Personal Identity (Fall 1999) / Notes / Identity in general

Identity in general

30 September

The main points

The goal of this class was to discuss identity in general. We want our discussions of personal identity to focus on what is unique about the identity of persons. Personal identity will be problematic in many of the ways that brick identity is problematic. But we want to isolate what's distinctive about the case of persons (or show that, contrary to appearances, there really isn't anything distinctive about them. Furthermore, we want to avoid saying things about persons that would conflict with apparently obvious points about identity in general.

Two important points are:

  1. Identity is a relation: we're always asking whether A is the same as B and it's usually confusing to talk as if identity is something that could exist such that, say, A could retain its identity. "A retains its identity" means A still exists; the only alternative to "remaining identical" is ceasing to exist. So, if you've got "identity" in a sentence, there should be nouns or names on either side. If you find "A retains its identity" in a draft, replace it with "A continues to exist."
  2. We have to be clear on this issue: "identity of what?" We have to specify what it is that we're talking about when we ask an identity question. Everyday pointing to objects is ambiguous: is this the same as the one that was here last week? Same what? Same table, same collection of molecules, same bit of University of Chicago property?

Distinctions and platitudes

You should feel very comfortable with these. If you don't, learn them right away.

First, some distinctions:

  1. Identity at a time vs. identity over time.
  2. Qualitative identity vs. numerical identity

We will almost always be talking about the latter in both cases.

Platitudes about identity are apparently obvious points; if our account of personal identity contradicts one of these, we'd better have a very good reason for sticking with it.

  1. Identity is the relation everything has to itself and to nothing else.
  2. There is a distinction between qualitative identity and numerical identity.
  3. Most things can undergo some kinds of change and remain the same (a tree can lose a limb and remain the same tree).
  4. Nothing can be in two places at the same time; no two things of the same kind can be in the same place at once.
  5. One thing cannot have two beginnings.


According to Locke, the fundamental building blocks of the universe are substances and modes of substances. But one hunk of substance can constitute several things: a mass of matter and a horse are made up of the same matter, at any given moment in time. The horse has a kind of unity over time by virtue of being a life that enables it to survive the loss or addition of matter, whereas the mass of matter does not.

Locke's account of animal and plant life is very important, in addition to being quite interesting in its own right. Locke thinks personal identity over time is analogous to animal identity over time.

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Copyright by Michael J. Green, except where noted.

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