The expression commonly employed, “history of philosophy,” often seems either inexact or incomplete, depending on whether the term “philosophy” is understood to mean a system of the sciences or whether it is taken in the historic sense. In the first case, what is in question is a certain ideal system of well-founded questions and of exact and logically demonstrated affirmations relative to the objects of a certain domain. So defined, philosophy is not the object of this study. In the second case, the historic sense, the term “philosophy” designates a collection of questions and affirmations growing and changing in time, effectively expressed in a given time and by specific men. They ought to concern the objects of the domain of philosophy in the sense of systematic exposition, whose content, however, itself underwent notable changes in the course of the development of philosophy in the historical sense—particularly of European philosophy. In the spirit of their authors they ought to be true. However, according to all probability, many of them are false or at least insufficiently founded. They are, moreover, the intentional products of a certain number of cognitive, human acts. But they result at the same time—in their properties, their content, their formulation, the mode of their justification—from the influence of other states and extra-cognitive attitudes of philosophers: various sentiments, desires, religious beliefs, etc. It is therefore improper to speak of the “history of philosophy” in the sense of a philosophic system, for, in this sense, philosophy insofar as it is an ideal, extratemporal product can have no kind of history. If, on the other hand, this expression is intended to involve a question of philosophy in the historic sense, it is necessary to complete it by specifying that in the given historic consideration we are dealing with the evolution of a given philosophy—for example, of Greek philosophy from Thales to the death of Aristotle. So understood, the history of philosophy is an empirical discipline relative to certain empirical facts which occur in time. It is necessary to bear clearly in mind the nature of these acts: Is it a question only of a certain collection of phrases, or of something more?