Artistic and literary history cannot dispense with the criterion of progress any more easily than other history. We cannot show what a given work of art is, save by proceeding from a conception of art, in order to fix the artistic problem which the author of such work of art had to solve, and by determining whether or no he have solved it, or by how much and in what way he has failed to do so. But it is important to note that the criterion of progress assumes a different form in artistic and literary history to that which it assumes (or is believed to assume) in the history of science. The whole history of knowledge can be represented by one single line of progress and regress. Science is the universal, and its problems are arranged in one single vast system, or complex problem. All thinkers weary themselves over the same problem as to the nature of reality and of knowledge: contemplative Indians and Greek philosophers, Christians and Mohammedans, bare heads and heads with turbans, wigged heads and heads with the black berretta (as Heine said); and future generations will weary themselves with it, as ours has done. It would take too long to inquire here if this be true or not of science. But it is certainly not true of art; art is intuition, and intuition is individuality, and individuality is never repeated. To conceive of the history of the artistic production of the human race as developed along a single line of progress and regress, would therefore be altogether erroneous.