It may seem that in this way we destroy all idea of philosophic progress; and certainly philosophy, taken in itself, that is to say as an abstract category, does not progress any more than the category of art or of morality progresses. But philosophy in its concreteness progresses, like art and the whole of life; it progresses, because reality is development, and development, including antecedents in consequences, is progress. Every affirmation of truth is conditioned by reality and conditions a new reality, which, in turn, is in its progress, the condition of a new thought and of a new philosophy. In this respect it is true that a philosophy which comes later in time, contains the preceding philosophies in itself, and not only when it is truly a philosophy, adequate to the new times, which comprehend ancient times in themselves, but even when it is a simple suggestion, of the kind we have called erroneous and in need of correction. As erroneous suggestion it will be, ideally, inferior to the truths already discovered. The scepticism of David Hume, for instance, is inferior from this point of view, not only to Cartesianism, but even to Scholasticism, to Platonism and to Socraticism. But historically it is superior even to the most perfect of those philosophies, because it is occupied with a problem which they did not propose to themselves and initiates its solution, by forming a first attempt at solution, however erroneous. Those perfect philosophies belong to the past, this, though imperfect, has the future in itself. Thus it is explained how we sometimes find far more to learn in philosophers who have maintained errors than from others who have maintained truths; the errors of the former are gold in the quartz, which when it has been purified will add weight and value to the mass of gold, which is already in our possession and has been preserved by the latter. Fanatics content themselves with truths, however poor they are, and therefore seek those who repeat them, even though they be poor of spirit. True thinkers seek for adversaries, bristling with errors and rich with truth; they learn from them, and while opposing, love and esteem them; indeed, their opposing them is at the same time an act of esteem and of love. [Sidenote: _The truth of all philosophies, and critique of eclecticism._]