There are some quite striking similarities between the moral psychology Maimonides presents in ‘Eight Chapters’ and Aristotle's moral psychology. They both deny that individuals have the virtues and vices by nature; they put a great deal of weight on habituation as a formative factor with respect to character; and they both characterize virtues in terms of lying in a mean between excess and defect. These are fundamentals of moral psychology that they share. But there are some very significant differences as well, and these are brought out quite clearly by a consideration of Maimonides' ‘Laws of Repentance’. It is worth looking at these differences not just for the sake of seeing how some Aristotelian claims are modified by the Jewish tradition, but also in order to see how moral psychology and the interpretation of the scope of human volition are altered by certain types of theistic commitments.