[209] Again, of things on earth, sweet water is opposite to bitter, and barren to fertile land. Again, there are other things contrary to one another, as visible bodies to incorporeal, things endowed with vitality to things inanimate, rational to irrational, mortal to immortal, things discernible by the outward sense to things perceptible only by the intellect; [141] [142] things comprehensible to things incomprehensible, elements to things concrete and perfected, beginning to end, generation to destruction, life to death, disease to health, white to black, the right to the left, justice to injustice, wisdom to folly, courage to cowardice, temperance to intemperance, virtue to vice; and all the species of one class to all the species of the other class.