The special subject of the greater part of the letters and essays of Schiller contained in this volume is Aesthetics; and before passing to any remarks on his treatment of the subject it will be useful to offer a few observations on the nature of this topic, and on its treatment by the philosophical spirit of different ages. First, then, aesthetics has for its object the vast realm of the beautiful, and it may be most adequately defined as the philosophy of art or of the fine arts. To some the definition may seem arbitrary, as excluding the beautiful in nature; but it will cease to appear so if it is remarked that the beauty which is the work of art is higher than natural beauty, because it is the offspring of the mind. Moreover, if, in conformity with a certain school of modern philosophy, the mind be viewed as the true being, including all in itself, it must be admitted that beauty is only truly beautiful when it shares in the nature of mind, and is mind's offspring.