From this double consideration of the nature of error, first, as error which is conquered and comprehended by truth, and then as attempt or hypotheses in the service of truth, Croce derives the identification of the history of error with the history of truth, or philosophy. But not in the sense in which Hegel had considered the successive apparition of the various philosophical categories and of the various forms of error, seeing in them a kind of gradual revelation of his own philosophy. To Croce such a conception of the progress of philosophy is unacceptable. Philosophy as an abstract category, as one of the forms of the spiritual activity, has no origin in time, is not limited to the men we call philosophers, but acts in every moment of the life of the spirit on the material offered by history, which it contributes to create, and does not, therefore, progress any more than the categories of art or of morality. But it progresses in its concreteness, as art and the whole of life do; because life is development, and development is progress. Every affirmation of reality is conditioned by reality and conditions a new reality, which in its turn is, in its progress, the condition of a new thought and a new philosophy. In this perpetual cycle, though individual errors are conquered, no form of error can be definitely abolished; but they constantly reappear, because of the intrinsic necessity of their structure, and when they reappear not as wilful errors, but as attempts and hypotheses, they have their appointed function in the progress of truth and reality. To this constancy of error corresponds a constancy of truth: truth is not attained once and for ever, but is true in the act of its affirmation, and in proportion to its adequacy to the particular problem, to the individual conditions of fact, which necessarily include, at every given moment, the whole history of the past. Thus, from a different angle, Croce's theory of error reaches the same conclusion as his general theory of logic, the identity of philosophy and history; and philosophy appears as a perpetual development, a history that never can repeat itself, since every affirmation of the truth transforms itself into a new element of reality, into one of the conditions determining every new problem and every new solution. [Footnote 1: See _Logica_, part iii, "Le forme degli errori," etc., pp. 271-421.] VIII. THE PRACTICAL ACTIVITY[1]