There are two forms of knowledge: intuitive (or æsthetic) and conceptual (or logical). Intuition is the knowledge of the individual or particular; the concept is the knowledge of the universal. This distinction, as we have already seen, corresponds roughly to the old classical distinction of _mythos_ and _logos_, to Vico's definitions of poetry and metaphysics, and to the new meaning given by Baumgarten to the old antithesis of _aisthēta_ and _noēta_. Let us quote Vico again: "Men first feel without perceiving, then they perceive and are perturbed and moved; finally they reflect with pure mind." Here we have three successive grades, of which the first is mere sensation, the lower limit of mental activity; the second is intuition; the third, concept. For Vico, the second grade is identical with Poetry, and the science of this form of knowledge, which we call Æsthetics, he called Poetic Logic, the science of poetry as "the first operation of the human mind." Vico's discovery consists in this definition of Poetry (and Art), not as a casual, capricious, lateral form of spiritual activity, but as the first and necessary grade of knowledge, as an essential function of the mind. But Vico's thought was clothed in what we might well call a mythological form: the various grades of spiritual activity were presented by him as successive stages or epochs in the history of mankind; and the inter-relation of the various grades, as the actual law of the development of human society. Croce unravelled Vico's philosophy, or ideal history, history of the mind, from Vico's concrete, sociological history, and the result was this new Æsthetics which is at the same time a science of the first grade of knowledge, and of art and language.