The conventional statement that experience only tells us how men have thought or _do_ think, while logic is concerned with norms, with how men _should_ think, is ludicrously inept. Some sorts of thinking are shown _by_ experience to have got nowhere, or worse than nowhere--into systematized delusion and mistake. Others have proved in manifest experience that they lead to fruitful and enduring discoveries. It is precisely in experience that the different consequences of different methods of investigation and ratiocination are convincingly shown. The parrot-like repetition of the distinction between an empirical description of what is and a normative account of what should be merely neglects the most striking fact about thinking as it empirically is--namely, its flagrant exhibition of cases of failure and success--that is, of good thinking and bad thinking. Any one who considers this empirical manifestation will not complain of lack of material from which to construct a _regulative_ art. The more study that is given to empirical records of actual thought, the more apparent becomes the connection between the specific features of thinking which have produced failure and success. Out of this relationship of cause and effect as it is empirically ascertained grow the norms and regulations of an art of thinking. Mathematics is often cited as an example of purely normative thinking dependent upon _a priori_ canons and supra-empirical material. But it is hard to see how the student who approaches the matter historically can avoid the conclusion that the status of mathematics is as empirical as that of metallurgy. Men began with counting and measuring things just as they began with pounding and burning them. One thing, as common speech profoundly has it, led to another. Certain ways were successful--not merely in the immediately practical sense, but in the sense of being interesting, of arousing attention, of exciting attempts at improvement. The present-day mathematical logician may present the structure of mathematics as if it had sprung all at once from the brain of a Zeus whose anatomy is that of pure logic. But, nevertheless, this very structure is a product of long historic growth, in which all kinds of experiments have been tried, in which some men have struck out in this direction and some in that, and in which some exercises and operations have resulted in confusion and others in triumphant clarifications and fruitful growths; a history in which matter and methods have been constantly selected and worked over on the basis of empirical success and failure.