Amongst the special sciences treated by Aristotle, the Physics is contained in a whole series of physical treatises, which form a tolerably complete system of what constitutes the Philosophy of Nature in its whole extent. We shall try to give their general plan. Aristotle’s first work is his Treatise, in eight books, on Physics, or on the Principles (φυσικὴ ἀκρόασις ἢ περὶ ἀρχῶν). In this he deals, as is fitting, with the doctrine of the Notion of nature generally, with movement, and with space and time. The first manifestation of absolute substance is movement, and its moments are space and time; this conception of its manifestation is the universal, which realizes itself first in the corporeal world, passing into the principle of separation. Aristotle’s Physics is what for present physicists would, properly speaking, be the Metaphysics of Nature; for our physicists only say what they have seen, what delicate and excellent instruments they have made, and not what they have thought. This first work by Aristotle is followed by his treatises concerning the Heavens, which deal with the nature of body and the first real bodies, the earth and heavenly bodies in general, as also with the general abstract relation of bodies to one another through mechanical weight and lightness, or what we should call attraction; and finally, with the determination of abstract real bodies or elements. Then follow the treatises on Production and Destruction, the physical process of change, while formerly the ideal process of movement was considered. Besides the physical elements, moments which are only posited in process, as such, now enter in: for instance, warmth, cold, &c. Those elements are the real existent facts, while these determinations are the moments of becoming or of passing away, which exist only in movement. Then comes the Meteorology; it represents the universal physical process in its most real forms. Here particular determinations appear, such as rain, the saltness of the sea, clouds, dew, hail, snow, hoar-frost, winds, rainbows, boiling, cooking, roasting, colours, &c. On certain matters, such as the colours, Aristotle wrote particular treatises. Nothing is forgotten, and yet the presentation is, on the whole, empiric. The book On the Universe, which forms the conclusion, is said not to be genuine; it is a separate dissertation, addressed to Alexander, which contains in part the doctrine of the universality of things, a doctrine found already in the other treatises; hence this book does not belong to this series.