Philosophy, throughout its history, has consisted of two parts inharmoniously blended: on the one hand a theory as to the nature of the world, on the other an ethical or political doctrine as to the best way of living. The failure to separate these two with sufficient clarity has been a source of much confused thinking. Philosophers, from Plato to William James, have allowed their opinions as to the constitution of the universe to be influenced by the desire of edification: knowing, as they supposed, what beliefs would make men virtuous, they have invented arguments, often very sophistical, to prove that these beliefs are true. For my part I reprobate this kind of bias, both on moral and on intellectual grounds. Morally, a philosopher who uses his professional competence for anything except a disinterested search for truth is guilty of a kind of treachery. And when he assumes, in advance of inquiry, that certain beliefs, whether true or false, are such as to promote good behaviour, he is so limiting the scope of philosophical speculation as to make philosophy trivial; the true philosopher is prepared to examine all preconceptions. When any limits are placed, consciously or unconsciously, upon the pursuit of truth, philosophy becomes paralyzed by fear, and the ground is prepared for a government censorship punishing those who utter 'dangerous thoughts'—in fact, the philosopher has already placed such a censorship over his own investigations.