There is certainly a history of ideas; but this does not consist in the vicious circle of ideas that explain themselves. It lies in rising from things to the idea. There is a problem; still more, there is a multitude of problems, so varied, multiple, multiform and mingled are the projections which men have made of themselves and of their economic-social conditions, and thus of their hopes and their fears, of their desires and their deceptions, in their artistic and religious concepts. The method is found, but the particular execution is not easy. We must above all guard against the scholastic temptation of arriving by deduction at the products of historic activity which are displayed in art and in religion. We must hope that philosophers like Krug, who explained the pen with which he wrote by a process of dialectic deduction, have remained forever buried in the notes of Hegel's logic. Here I must state certain difficulties. Before attempting to reduce secondary products (for example, art and religion) to the social conditions which they idealize, one must first acquire a long experience of specified social psychology, in which the transformation is realized. Therein consists the justification of that sum of relations, which is designated in another form of language, under the name of Egyptian _world_, Greek _consciousness_, _spirit_ of the Renaissance, _dominant ideas_, _psychology of nations_, of society or of classes. When these relations are established, and men have become accustomed to certain conceptions and certain modes of belief or of imagination, the ideas transmitted by tradition tend to become crystallized. Thus they appear as a force which resists new formations; and as this resistance shows itself through the spoken word, through writing, through intolerance, through polemics, through persecution, so the struggle between the new and the old social conditions takes on the form of a struggle between ideas. In the second place, through the centuries of history properly so-called, and as a consequence of the heredity of the pre-history of savagery and of the conditions of subjection and those of inferiority in which the majority of men were and are placed, resulted acquiescence in what is traditional, and the ancient tendencies are perpetuated as obstinate survivals.