‘He is truly great who knows the value of everything, and distinguishes what is more or less great, and what is most estimable, so as to begin from that, and to apply the genius, and fix the desires upon the execution of things worthy and great.’ This mode of thinking was followed by the most celebrated and enlightened artists from the ancient Greeks to our own time. They knew to distinguish that which was most worthy in nature, and to this they directed their study, diligence, and industry. Inferior geniuses, because they are attached to mediocrity, believe that a mere clinging to nature constitutes all art; and the lowest artists are enchanted with the minutiæ of little works, taking them for principal things; so that human ignorance passes from the trifling to the useless, from the useless to the ugly, and from the ugly to the false and chimerical. In treating of the historical development of art, to enable artists to distinguish and to choose the best, and not only to imitate but to create consciously for themselves, it is necessary to make them _theoretically_ acquainted with the progress of art. To trace historically the changes art had to undergo is necessary for all really self-conscious artists. Art with us is still looked upon as entirely subject to individual taste. Everyone thinks himself competent to have an opinion on products of art. ‘_De gustibus non est disputandum_’ is heard not only in our drawing-rooms, but also in art-circles. This false and utterly untenable adage is the cause of the chaotic anarchy in our art-world. So little as there can be differences in truth, can there be differences in beauty. It is the duty of philosophy to strive for truth; it is the task of the theoretical artist to point out what is beautiful. We may treat art from three different points of view:-- 1. From a _realistic_ point of view, taking nature and geometry as its basis. 2. From an _historical_ point of view; showing by antiquarian and archæological researches its gradual development. 3. From a _critical_ point of view; propounding abstract principles of speculative philosophy and esthetics as applied to art. A.