The difference of the first two is obvious. The history of art and literature has the works of art themselves as its principal subject; those other labours invoke and interrogate works of art, but only as witnesses from whom to discover the truth of facts which are not æsthetic. The second difference to which we have referred may seem less profound. It is, however, very great. Erudition directed to illuminate the understanding of works of art aims simply at calling into existence a certain internal fact, an æsthetic reproduction. Artistic and literary history, on the other hand, does not appear until after such reproduction has been obtained. It implies, therefore, a further stage of labour. Like all other history, its object is to record precisely such facts as have really taken place, in this case artistic and literary facts. A man who, after having acquired the requisite historical erudition, reproduces in himself and tastes a work of art, may remain simply a man of taste, or at the most express his own feeling with an exclamation of praise or condemnation. This does not suffice for the making of a historian of literature and art. Something else is needed, namely, that a new mental operation succeed in him the simple reproduction. This new operation is in its turn an expression: the expression of the reproduction; the historical description, exposition or representation. There is this difference, then, between the man of taste and the historian: the first merely reproduces in his spirit the work of art; the second, after having reproduced it, represents it historically, or applies those categories by which, as we know, history is differentiated from pure art. Artistic and literary history is therefore _a historical work of art founded upon one or more works of art._