Does the material constitution of an object determine its identity?

The material particles alone (what Peter van Inwagen describes as partless "simples") are nothing more than a "mereological sum." They do not "compose" an integrated "whole" unless we know something about the teleonomic process that created and maintains the object.

It is the matter plus the form that informs us about an object's identity. In general, we cannot have matter without form. But this raises the problem of recognizing a dualist idealism that has as much reality as pure materialism.

Given a lump of material, it is the form as a function of time that allows us to study change and the object's persistence conditions over time.

It is arguably the colocation of form and matter that has generated several of the ancient puzzles that are still plaguing analytic language metaphysicians, problems like the Statue and Lump of Clay, the Ship of Theseus, the Problem of the Many, and Dion and Theon (a/k/a Tibbles the Cat).

A materialist metaphysics asks questions about the underlying substrate that constitutes all the objects in the universe. Unfortunately, most modern philosophers think that the material substrate is all there is. As Jaegwon Kim puts it,

"bits of matter and their aggregates in space-time exhaust the contents of the world. This means that one would be embracing an ontology that posits entities other than material substances — that is, immaterial minds, or souls, outside physical space, with immaterial, nonphysical properties."

(Physicalism, or Something Near Enough, p. 71)

But clearly the form of an object – the information it contains – plays a major role in identity, if not the dominant role for identity over time.

Because all material things change in time (the Heraclitean "flux" or Platonic "Becoming"), the concept of "identity over time" is fundamentally flawed. Even in the case of a hypothetical completely inert object that could be protected from loss or gain of a single particle, its position coordinates in most spacetime frames are constantly changing.

Perfect identity over time is limited to unchanging ideas or concepts – Parmenidean "Being." These are some of the abstract entities, like numbers and logical truths.

But identity over time "in some respects" is always available. Instead of plus ça change, plus c'est la même chose, we have la change á tout le temps, et seulement la même chose á la même temps.

We can assert three axioms about identity:

Id1. Everything is identical to everything else in some respects.

Id2. Everything is different from everything else in some other respects.

Id3. Everything is identical to itself in all respects at each instant of time, but different in some respects from itself at any other time.

For biological entities, complete identity should include the practically inaccessible knowledge of all stored information (memories of experiences) and all the instantaneous communications of information between the organism's proper parts (from the cell to the mental level)