This conception, or rather misconception, of opposites appears most curiously in two of the proofs which Socrates offers for the immortality of the soul, and I do not know how I can better illustrate the infirmity of antique thought which I have just been describing than by citing the arguments of Socrates in that connection according to the Phædo. Socrates introduced it with special solemnity. "I do not imagine," he says, "that any one, not even if he were a comic poet, would now say that I am trifling.... Let us examine it in this point of view, whether the souls of the dead survive or not.
"Let us consider this, whether it is absolutely necessary in the case of as many things as have a contrary, that this contrary should arise from no other source than from a contrary to itself. For instance, where anything becomes greater, must it not follow that from being previously less it subsequently became greater?
"Yes."
"So, too, if anything becomes less, shall it become so subsequently to its being previously greater?"
"Such is the case," said Cebes.
"And weaker from stronger, swifter from slower, ... worse from better, juster from more unjust?"
"Surely."
"We are then sufficiently assured of this, that all things are so produced, contraries from contraries?"
"Sufficiently so."