To Florus 1.44

What then? I will indeed yield to you. At this point I will give up everyone whose support I could use and be content with a definition which, as evidence of a good nature, escaped from your honorable mouth after you left the secret company of the Manichaeans. In the book entitled either On Two Souls or Against Two Souls, you say: “Wait; let us first define sin. Sin is the will to commit or retain something justice forbids and from which one is free to abstain. In fact, if one is not free, it cannot even be called will; but I preferred a rougher definition to a more exacting one” (Augustine, On Two Souls 15).