But that is not all; there is much more in the way of preliminaries: there must be a general “expurgation of the intellect.” The mind is full (some would say made up) of prejudices, wild fancies, “idols,” or imaginings of things that are not so: if you are to think correctly, usefully, all these must go. Try, then, to get as little of yourself as possible in the way of the thing you wish to see. Beware of the very general tendency to put order and regularity in the world and then to suppose that they are native to the structure of things; or to force all facts into the unyielding mould of a preconceived opinion, carefully neglecting all contrary instances; or to give too credulous an ear to that which flatters the wish. Look into yourself and see the forest of prejudices that has grown up within you: through your temperamental attitudes; through your education; through your friends (friendship is so often an agreement in prejudices); through your favorite authors and authorities. If you find yourself seizing and dwelling on anything with particular satisfaction, hold it in suspicion. Beware of words, for they are imposed according to the apprehension of the crowd; make sure that you do not take abstractions for things. And remind yourself occasionally that you are not the measure of all things, but their distorting mirror. So much by way of clearing the forest. Comes then induction as the fount and origin of all truth: patient induction, obedient to the call of fact, and with watchful eye for, above all things, the little unwelcome instance that contradicts. Not that induction is everything; it includes experiment, of course, and is punctuated by hypothesis.[54] (More, it is clearly but the servant of deduction, since the aim of all science is to predict by deduction from generalizations formed by induction; but just as clear is it that the efficacy of the whole business lies grounded in the faithfulness of the induction: induction is servant, but it has all men at its mercy.) And to formulate methods of induction, to surround the process by mechanical guards, to protect it from the premature flights of young generalizations,--that is a matter of life and death to science. IV Knowledge is Power And now, armed with these methods of procedure, we stand face to face with nature. What shall we ask her? _Prudens questio dimidium scientiæ_: to know what to ask is half of every science.