Composition as identity is the strange and strangely compelling doctrine that the whole is in some sense identical to its parts. According to the most interesting and fun version, the one inspired by Donald Baxter (19882,b), this is meant in the most straightforward way: a single whole is genuinely identical to its many parts, in the very same sense of identity, familiar to philosophers, logicians, and mathematicians, in which I am identical to myself and 2 + 2 is identical to 4.