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