The Aristotelian logic is far from having withdrawn its claim. It still offers its framework as that into which the merely "empirical" results of observation and experimental inquiry must be fitted if they are to be regarded as really "proved." Another school of logicians, starting professedly from modern psychology, discredits the whole traditional industry and reverses the Aristotelian theory of validity; it holds that only particular facts are self-supporting, and that the authority allowed to general principles is derivative and second hand. A third school of philosophy claims, by analysis of science and experience, to justify the conclusion that the universe itself is a construction of thought, giving evidence throughout of the pervasive and constitutive action of reason, and holds, consequently, that our logical processes are simply the reading off or coming to consciousness of the inherently rational structure already possessed by the universe in virtue of the presence within it of this pervasive and constitutive action of thought. It thus denies both the claim of the traditional logic, that matters of experienced fact are mere particulars having their rationality in an external ground, and the claim of the empirical logic, that thought is just a gymnastic by which we vault from one presented fact to another remote in space and time. Which of the three doctrines is to be regarded as the legitimate exponent of the procedure of thought manifested in modern science? While the Aristotelian logic is willing to waive a claim to be regarded as expounder of the actual procedure, it still insists upon its right to be regarded as the sole ultimate umpire of the validity or _proved_ character of the results reached. But the empirical and transcendental logics stand face to face as rivals, each asserting that it alone tells the story of what science does and how it does it.