Plotinus, in his treatise _On the Beautiful_,[105] proposed to himself this question. He asks--What is the beautiful in itself? I see clearly that such or such a form is beautiful, that such or such an action is also beautiful; but why and how are these two objects, so dissimilar, beautiful? What is the common quality which, being found in these two objects, ranges them under the general idea of the beautiful? It is necessary to answer this question, or the theory of beauty is a maze without issue; one applies the same name to the most diverse things, without understanding the real unity that authorizes this unity of name. Either the diversities which we have designated in beauty are such that it is impossible to discover their relation, or these diversities are especially apparent, and have their harmony, their concealed unity. Is it pretended that this unity is a chimera? Then physical beauty, moral beauty, and intellectual beauty, are strangers to each other. What, then, will the artist do? He is surrounded by different beauties, and he must make a work; for such is the recognized law of art. But if this unity that is imposed upon him is a factitious unity, if there are in nature only essentially dissimilar beauties, art deceives and lies to us. Let it be explained, then, how falsehood is the law of art. That cannot be; the unity that art expresses, it must have somewhere caught a glimpse of, in order to transport it into its works. We neither retract the distinction between the beautiful and the sublime, nor the other distinctions just now indicated; but it is necessary to re-unite after having distinguished them. These distinctions and these re-unions are not contradictory: the great law of beauty, like that of truth, is unity as well as variety. All is one, and all is diverse. We have divided beauty into three great classes--physical beauty, intellectual beauty, and moral beauty. We must now seek the unity of these three sorts of beauty. Now, we think that they resolve themselves into one and the same beauty, moral beauty, meaning by that, with moral beauty properly so called, all spiritual beauty. Let us put this opinion to the proof of facts.