Some say that the wizard believes in himself because all others believe in him; that at a certain level of culture, there is an universal social obsession by certain ideas, from which the individual cannot escape, and for whose consequences, therefore, he is not responsible. According to this theory, a sort of tribal insanity prevails. Dr. Mercier says that, in the individual, paranoia is characterised by systematised delusion: “there is an organised body of (false) knowledge, and it differs from other delusions in the fact that it colours the whole life of the patient; it regulates his daily conduct; it provides him with an explanation of all his experiences; it is his theory of the cosmos.” And, again, “as long as the highest level of thought is intact, so that we can and do recognise that our mistakes are mistakes and our disorders, whether of mind or conduct, are disorders, so long sanity is unaffected, and our mistakes and disorders are sane. As soon, however, as we become incompetent to make this adjustment ... insanity is established.”[468] These passages exactly describe the condition of a wizard and his tribe afflicted with social paranoia: their theories of Magic and Animism and of the wizard’s relations with invisible powers, may truly be said to form an organised body of (false) knowledge, to colour all their lives, to explain everything that happens to them; and their mistakes and disorders to be incorrigible by reflection or experience. Such conditions of the social mind have, I believe, existed (and may still exist), tending toward, and sometimes ending in, a tribe’s destruction. That, in such a case, there should be unanimity is not necessary; it is enough that the current of belief, in certain directions, be overwhelming. But such extreme cases are rare. Normally there may be found, even in backward tribes, a good deal of incredulity and of what may be called primitive rationalism or positivism.