Summarily put, the waste and loss consequent upon the natural happening of inference led man, slowly and grudgingly, to the adoption of safeguards in its performance. In some part, the scope of which is easily exaggerated, man has come to attribute many of the ills from which he suffers to his own premature, inept, and unguarded performing of inference, instead of to fate, bad luck, and accident. In some things, and to some extent in all things, he has invented and perfected an art of inquiry: a system of checks and tests to be used before the conclusion of inference is categorically affirmed. Its nature has been considered in many other places in these pages, but it may prove instructive to restate it in this context. _a_) Nothing is less adapted to a successful accomplishing of an inference than the subject-matter from which it ordinarily fares forth. That subject-matter is a nest of obscurities and ambiguities. The ordinary warnings against trusting to imagination, the bad name which has come intellectually to attach to fancy, are evidences that anything may suggest anything. Regarding most of the important happenings in life no inference has been too extravagant to obtain followers and influence action, because subject-matter was so variegated and complex that any objects which it suggested had a prima facie plausibility. That every advance in knowledge has been effected by using agencies which break up a complex subject-matter into independent variables (from each of which a distinct inference may be drawn), and by attacking each one of these things by every conceivable tool for further resolution so as to make sure we are dealing with something so simple as to be unambiguous, is the report of the history of science. It is sometimes held that knowledge comes ultimately to a necessity of belief, or acceptance, which is the equivalent of an incapacity to think otherwise than so and so. Well, even in the case of such an apparently simple "self-evident" thing as a red, this inability, if it is worth anything, is a residuum from experimental analysis. We do not believe in the thing as red (whenever there is a need of scientific testing) till we have exhausted all kinds of active attack and find the red still resisting and persisting. Ordinarily we move the head; we shade the eyes; we turn the thing over; we take it to a different light. The use of lens, prism, or whatever device, is simply carrying farther the use of like methods as of physical resolution. Whatever endures all these active (not mental) attacks, we accept--pending invention of more effective weapons. To make sure that a given fact _is_ just and such a shade of red is, one may say, a final triumph of scientific method. To turn around and treat it as something naturally or psychologically given is a monstrous superstition.