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.