The relation between the theoretical and the practical activity is of the same kind as that between the two grades of the theoretical activity: that is, the first is the basis of the second. We can think of a knowing which is independent from the will, but not of a will which is independent of knowledge: it is impossible to will without historical intuitions and a knowledge of relations. Within the practical activity, we can further distinguish two grades corresponding to the two grades of the theoretical activity: the economic, which is the will of the individual, of a particular end, and the ethic, which is the will of the universal, of the rational end. The relation between the economic and the ethic activity is again the same grade-relation as between the æsthetic and the logic, the theoretical and the practical. The concrete life of the human spirit consists in the perpetually recurring cycle of the four grades of its activity, which is the law of its unity and development. The concept rises from the intuition, and action from knowledge; ethical activity is not conceivable without a theoretical foundation, and the concreteness of a particular end. At the close of the cycle, the spiritual life itself becomes the object of a new intuition, from which a new concept and a new action are reproduced _ad infinitum_. In the history of æsthetics, the errors deriving from the confusion of that which is distinctively æsthetic with other forms of theoretical or practical activity, present themselves as a series of doctrines, which can be considered as gradual approximations to the definition of art as intuition. It is not necessarily, or not only, a chronological series, but rather a succession of actual moments in the deduction of the concept of art. Empirical æsthetics recognises the existence of a class of æsthetic or artistic facts, without attempting to reduce them under a single concept; practical (hedonistic or moralistic) æsthetics makes a first attempt at interpreting them by putting them in relation with one of the categories of spiritual activity; intellectualiste æsthetics denies that they belong to the practical sphere, though failing to discover their precise theoretical character; agnostic æsthetics criticises all the preceding moments, and is satisfied with a purely negative definition; mystic æsthetics, conscious of the difference of æsthetic from logical facts, makes a new spiritual category of them, affirms their autonomy and independence, but mistakes the nature of their relation with conceptual knowledge. We are all more or less familiar with the various aspects of these doctrines, and it can be said that none of them (with the exception of the first, which is now represented by psychologic æsthetics) is now being held consistently by any responsible thinker. The truth of the intuitive theory, which we find adumbrated already in classical antiquity in the Aristotelian