I believe—and human psychologists, particularly psychoanalysts should test this—that present-day civilized man suffers from insufficient discharge of his aggressive drive. It is more than probable that the evil effects of the human aggressive drives, explained by Sigmund Freud as the results of a special death wish, simply derive from the fact that in prehistoric times intra-specific selection bred into man a measure of aggression drive for which in the social order today he finds no adequate outlet.

More about the selection theory: Jerne meant that the Socratic idea of learning was a fitting analogy for 'the logical basis of the selective theories of antibody formation': Can the truth (the capability to synthesize an antibody) be learned? If so, it must be assumed not to pre-exist; to be learned, it must be acquired. We are thus confronted with the difficulty to which Socrates calls attention in Meno [ ... ] namely, that it makes as little sense to search for what one does not know as to search for what one knows; what one knows, one cannot search for, since one knows it already, and what one does not know, one cannot search for, since one does not even know what to search for. Socrates resolves this difficulty by postulating that learning is nothing but recollection. The truth (the capability to synthesize an antibody) cannot be brought in, but was already inherent.

The resolution of revolutions is selection by conflict within the scientific community of the fittest way to practice future science. The net result of a sequence of such revolutionary selections, separated by periods of normal research, is the wonderfully adapted set of instruments we call modern scientific knowledge.