 Matter and form are required to account for this second kind of change, if it is to conform to Aristotle’s general conceptual analysis of change. In any change, he contends, there must be three things: (1) something which underlies and persists through the change; (2) a “lack”, which is one of a pair of opposites, the other of which is (3) a form acquired during the course of the change (Physics i 7, 190a13–191a22). Thus, for example, in an accidental change, the underlying thing is the substance which acquires a new accidental property. For instance, when Socrates learns to play the flute, he transitions from a state of being unmusical (the lack) to a state of musicality (the form). But for us to be able to say that there is something which has changed, there must be something which remains the same throughout the change, and in this case the obvious candidate is Socrates, who is one and the same person throughout his musical training.