XIX. (109) For this reason all animals with solid hoofs, and all with many toes are spoken of by implication as unclean; the one because, being so, they imply that the nature of good and evil is one and the same; which is just as if one were to say that the nature of a concave and a convex surface, or of a road up hill and down hill, was the same. And the other, because it shows that there are many roads, though, indeed, they have no right to be called roads at all, which lead the life of man to deceit; for it is not easy among a variety of paths to choose that which is the most desirable and the most excellent.