Concerning the Nature of Good, Against the Manichaeans

But that what we have said may be understood, and may satisfy those too slow of comprehension, or that even the pertinacious and those repugnant to the most manifest truth may be compelled to confess what is true, let them be asked, whether corruption can harm the body of an ape? But if it can, so that it may become more hideous, what diminishes but the good of beauty? Whence as long as the nature of the body subsists, so long something will remain. If, accordingly, good having been consumed, nature is consumed, the nature is therefore good.

So also we say that slow is contrary to swift, but yet he who does not move at all cannot even be called slow. So we say that a heavy voice is contrary to a sharp voice, or a harsh to a musical; but if you completely remove any kind of voice, there is silence where there is no voice, which silence, nevertheless, for the simple reason that there is no voice, is usually opposed to voice as something contrary thereto. So also lucid and obscure are called as it were two contrary things, yet even obscure things have something of light, which being absolutely wanting, darkness is the absence of light in the same way in which silence is the absence of voice.