In this paper I offer an ontological elucidation of change. In the first part, I examine two conceptions of change that can be found in Aristotle's Physics and I hold that one of them is more basic than the other. In the second part, I offer an ontological model of change according to which a change is a kind of conjunction of states and times.
According to Aristotle a change, metabolé, is from something to something else. He distinguishes three kinds of changes. One of them is what he calls motion- kinesis- i.e., the transition from a positive term A to a negative term B. Motion in respect to quality is called alteration, in respect to quantity it is known either as increase or as decrease, and in respect to place it is designated by the name of locomotion.