Émile Bréhier, The Philosophy of Plotinus, translated by Joseph Thomas (UChicago, 1958)
The history of philosophy does not reveal to us ideas existing in themselves, but only the men who think. Its method, like every historical method, is nominalistic. Ideas do not, strictly speaking, exist for it. It is only concrete and active thoughts that exist. The problems which philosophers pose and the solutions they offer are the reactions of original thought operating under given historical circumstances and in a given environment. It is permissible, no doubt, to consider ideas or the representations of reality which result from these reactions in isolation. But thus isolated, they are like effects without causes. We may indeed classify systems under general titles. But classifying them is not giving their history (182).
A true philosophical reform, such as that of a Socrates or of a Descartes, always takes for its point of departure a confrontation of the needs of human nature with the representation the mind forms of reality. It is the sense of a lack of correspondence between these needs and the representation which, in exceptionally endowed minds, awakens the philosophical vocation. Thus, little by little, philosophy reveals man to himself. It is the reality of his own needs, of his own inclinations, which forms the basis of living philosophical thought. A philosophy which does not give the impression of being indispensable to the period in which it appears is merely a vain and futile curiosity (pp. 183-4).