 A final reaction to the argument would be to reject the third premise, the idea that anything enmattered is a compound of its matter and form at a given time. Certainly the most straightforward way of understanding hylomorphism is that the compound is compounded of the thing’s matter and form at a particular time, and the relation between the compound and the thing is identity. This way of understanding composition is not only problematic because it leads to the problem currently under discussion: assuming that things can change their matter, we might well also wonder (a) how just one of the matters, which it has at a particular time, can yield the whole thing, and (b) how different matters at different times can yield the same thing. An alternative way to understand compounding would be to say that a thing is the compound of its form and all the various matters that it has at different times: \(X = F(m_1, m_2, \ldots m_n)\), where \(m_1\ldots m_n\) are \(X\)’s proximate matters in order of temporal occurrence. This would solve worries (a) and (b) above, since now all the different matter-slices are incorporated into the one object. It does not obviously help with the problem at hand, however, since, if it is possible for Socrates and Callias to have the same matter at a time, there seems to be no barrier to them having exactly the same sequence of matter-slices throughout their lives (provided that they are not born at the same time, and live to exactly the same age).