These sciences, it was admitted, command and deserve unqualified respect. To discover the secret of their success Kant passed in review their different systems, examined them in respect to their principles and conditions of progress, with a purpose to know what, if any, essential difference there might be between them and the metaphysics which had from of old claimed to be, and had the name of being, a science. Logic, mathematics, physics, are sciences: by virtue of what inherent peculiarity do they claim superior right to that high appellation? Intellectual philosophy has always been given over to conflicting parties. Its history is a history of controversies, and of controversies that resulted in no triumph for either side, established no doctrine, and reclaimed no portion of truth. Material philosophy has made steady advances from the beginning; its disputes have ended in demonstrations, its contests have resulted in the establishment of legitimate authority: if its progress has been slow it has been continuous; it has never receded; and its variations from a straight course are insignificant when surveyed from a position that commands its whole career.
Since Aristotle, logic has, without serious impediment or check, matured its rules and methods. Holding the same cardinal positions as in Aristotle's time, it has simply made them stronger, the rules being but interpretations of rational principles, the methods following precisely the indications of the human mind, which from the nature of the case remain always the same.
The mathematics, again, have had their periods of uncertainty and conjecture. But since the discovery of the essential properties of the triangle, the career has been uninterrupted. The persistent study of constant properties, which were not natural data, but mental conceptions formed by the elimination of variable quantities, led to results which had not to be abandoned.
It was the same with physics. The physics of the ancients were heaps of conjecture. The predecessors of Galileo abandoned conjecture, put themselves face to face with Nature, observed and classified phenomena, but possessed no method by which their labors could be made productive of cumulative results. But after Galileo had experimented with balls of a given weight on an inclined plane, and Torricelli had pushed upward a weight equal to a known column of water, and Stahl had reduced metals to lime and transformed lime back again into metal, by the addition and subtraction of certain parts, the naturalists carried a torch that illumined their path. They perceived that reason lays her own plans, takes the initiative with her own principles, and must compel nature to answer her questions, instead of obsequiously following its leading-string. It was discovered that scattered observations, made in obedience to no fixed plan, and associated with no necessary law, could not be brought into systematic form. The discovery of such a law is a necessity of reason. Reason presents herself before nature, holding in one hand the principles which alone have power to bring into order and harmony the phenomena of nature; in the other hand grasping the results of experiment conducted according to those principles. Reason demands knowledge of nature, not as a docile pupil who receives implicitly the master's word, but as a judge who constrains witnesses to reply to questions put to them by the court. To this attitude are due the happy achievements in physics; reason seeking—not fancying—in nature, by conformity with her own rules, what nature ought to teach, and what of herself she could not learn. Thus physics became established upon the solid basis of a science, after centuries of error and groping.
Wherefore now, asks Kant, are metaphysics so far behind logic, mathematics, and physics? Wherefore these heaps of conjecture, these vain attempts at solution? Wherefore these futile lives of great men, these abortive flights of genius? The study of the mind is not an arbitrary pursuit, suggested by vanity and conducted by caprice, to be taken up idly and relinquished at a moment's notice. The human mind cannot acquiesce in a judgment that condemns it to barrenness and indifference in respect to such questions as God, the Soul, the World, the Life to Come; it is perpetually revising and reversing the decrees pronounced against itself. It must accept the conditions of its being.
From a review of the progress of the sciences it appeared to Kant that their advance was owing to the elimination of the variable elements, and the steady contemplation of the elements that are invariable and constant, the most essential of which is the contribution made by the human mind. The laws that are the basis of logic, of the mathematics, and of the higher physics, and that give certitude to these sciences, are simply the laws of the human mind itself. Strictly speaking, then, it is in the constitution of the human mind, irrespective of outward objects and the application of principles to them, that we must seek the principle of certitude. Thus far in the history of philosophy the human mind had not been fairly considered. Thinkers had concerned themselves with the objects of knowledge, not with the mind that knows. They had collected facts; they had constructed systems; they had traced connections; they had drawn conclusions. Few had defined the relations of knowledge to the human mind. Yet to do that seemed the only way to arrive at certainty, and raise metaphysics to the established rank of physics, mathematics, and logic.
Struck with this idea, Kant undertook to transfer contemplation from the objects that engaged the mind to the mind itself, and thus start philosophy on a new career. He meditated a fresh departure, and proposed to effect in metaphysics a revolution parallel with that which Copernicus effected in astronomy. As Copernicus, finding it impossible to explain the movements of the heavenly bodies on the supposition of their turning round the globe as a centre, bethought him to posit the sun as a centre, round which the earth with other heavenly bodies turned—so Kant, perceiving the confusion that resulted from making man a satellite of the external world, resolved to try the effect of placing him in the position of central sway. Whether this pretension was justifiable or not, is not a subject of inquiry here. They may be right who sneer at it as a fallacy; they may be right who ridicule it as a conceit. We are historians, not critics. That Kant's position was as has been described, admits of no question. That he built great expectations on his method is certain. He anticipated from it the overthrow of hypotheses which, having no legitimate title to authority, erected themselves to the dignity of dogmas, and assumed supreme rank in the realm of speculation. That it would be the destruction of famous demonstrations, and would reduce renowned arguments to naught, might be foreseen; but in the place of pretended demonstrations, he was confident that solid ones would be established, and arguments that were merely specious would give room to arguments that were profound. Schools might be broken up, but the interests of the human race would be secured. At first it might appear as if cardinal beliefs of mankind must be menaced with extinction as the ancient supports one after another fell; but as soon as the new foundations were disclosed it was anticipated that faith would revive, and the great convictions would stand more securely than ever. Whatever of truth the older systems had contained would receive fresh and trustworthy authentication; the false would be expelled; and a method laid down by which new discoveries in the intellectual sphere might be confidently predicted.
In this spirit the author of the transcendental philosophy began, continued, and finished his work.
The word "transcendental" was not new in philosophy. The Schoolmen had used it to describe whatever could not be comprehended in or classified under the so-called categories of Aristotle, who was the recognized prince of the