What ought we to make of Aristotle's apparently disparate comments on bodies in motion? I argue that Aristotle is concerned with a higher level project than dynamics and that is the establishment of a coherent theory of change in general. This theory is designed to avoid the paradoxes and infinities that Aristotle finds in Eleatic, Heraclitean and atomist accounts, notably in relation to comparatives such as 'quicker' and 'slower'. This theory relies on a broad application of proportionality to all types of change, not merely those we would label 'dynamics'. To support this I argue that Aristotle denied the existence of the void and the possibility of instantaneous change, and that he could accommodate 'threshold' changes within his scheme. If this is so, then the aims of Aristotle's comments on motion become more comprehensible, and it will be understandable why Aristotle was more concerned with the application of proportionality in general rather with the investigation of specific cases in dynamics.