Montaigne and Proust know human nature because they are in themselves several different men, because there are few human feelings, already existing in embryo in themselves, that they cannot experience if they set out to do so. They have that spider's web kind of sensibility which enables them to penetrate another person's defences and discover exactly how he feels. It is a polymorphous sensibility which is the only true source of ideas in psychology, but which, in those who possess it, makes the acquisition of a personal equilibrium a difficult and always precarious business. Or rather, the equilibrium is constantly being broken from day to day, but the continuous rupture is simply the raw material of a general equilibrium extending over the whole of existence. We might say of both of them that out of days as psychopaths they constructed the lives of sages.