The attitude of research is necessarily toward the future. The application of science to the practical affairs of life, as in the stationary engine, or telephone, does not differ in principle from the determination of wave-lengths of light through the experimental control of the laboratory. Science lives only in arranging for new contacts, new insights. The school of Kant agrees with that of Mill in asserting that judgment must, in order to be judgment, be synthetic or instructive; it must extend, inform, and purvey. When we recognize that this service of judgment in effecting growth of experience is not accidental, but that judgment means exactly the devising and using of suitable instrumentalities for this end, we remark that the so-called practical uses of science are only the further and freer play of the intrinsic movement of discovery itself. * * * * * We began with the assumption that thought is to be interpreted as a doubt-inquiry function, conducted for the purpose of arriving at that mental equilibrium known as assurance or knowledge. We assumed that various stages of thinking could be marked out according to the amount of play which they give to doubt, and the consequent sincerity with which thinking is identified with free inquiry. Modern scientific procedure, as just set forth, seems to define the ideal or limit of this process. It is inquiry emancipated, universalized, whose sole aim and criterion is discovery, and hence it marks the terminus of our description. It is idle to conceal from ourselves, however, that scientific procedure as a practical undertaking, has not as yet reflected itself into any coherent and generally accepted theory of thinking, into any accepted doctrine of logic which is comparable to the Aristotelian. Kant's conviction that logic is a "complete and settled" science, which with absolutely "certain boundaries has gained nothing and lost nothing since Aristotle," is startlingly contradicted by the existing state of discussion of logical doctrine. The simple fact of the case is that there are at least three rival theories on the ground, each claiming to furnish the sole proper interpretation of the actual procedure of thought.