Shaw's notion of life force, heavily influenced by thinkers such as Friedrich Nietzsche and especially Henri Bergson, was a central feature of Man and Superman. The idea was that human existence was driven by a "life force" that was a drive toward creating "supermen" through a process of evolutionary improvement that would advance the species. As Don Juan says in Act III of Shaw's Man And Superman:
Life is a force which has made innumerable experiments in organizing itself; that the mammoth and the man, the mouse and the megatherium, the flies and the fleas and the Fathers of the Church, are all more or less successful attempts to build up that raw force into higher and higher individuals, the ideal individual being omnipotent, omniscient, infallible, and withal completely, unilludedly self-conscious: in short, a god?
One example of this was that many of the social conventions governing interaction between men and women were essentially a cover for the drive to reproduce. Hence women wanted to marry accomplished, powerful, and intellectually fit men rather than kind men who would necessarily be good to them. Additionally, those who are viewed by society as having low morals (because of sexual activity) are in fact fulfilling the basic urge of the species, to create what the devil calls "the latest in fashion among Life Force fanatics," a Superman at the apogee of evolution.