It was the eighteenth century that introduced, or rather brought back into philosophy, investigations on the beautiful and art, so familiar to Plato and Aristotle, but which scholasticism had not entertained, to which our great philosophy of the seventeenth century had remained almost a stranger.[96] One comprehends that it did not belong to the empirical school to revive this noble part of philosophic science. Locke and Condillac did not leave a chapter, not even a single page, on the beautiful. Their followers treated beauty with the same disdain; not knowing very well how to explain it in their system, they found it more convenient not to perceive it at all. Diderot, it is true, had an enthusiasm for beauty and art, but enthusiasm was never so ill placed. Diderot had genius; but, as Voltaire said of him, his was a head in which every thing fermented without coming to maturity. He scattered here and there a mass of ingenious and often contradictory perceptions; he has no principles; he abandons himself to the impression of the moment; he knows not what the ideal is; he delights in a kind of nature, at once common and mannered, such as one might expect from the author of the _Interpretation de la Nature_, the _Pere de Famille_, the _Neveu de Rameau_, and _Jacques le Fataliste_. Diderot is a fatalist in art as well as in philosophy; he belongs to his times and his school, with a grain of poetry, sensibility, and imagination.[97] It was worthy of the Scotch[98] school and Kant[99] to give a place to the beautiful in their doctrine. They considered it in the soul and in nature; but they did not even touch the difficult question of the reproduction of the beautiful by the genius of man. We will try to embrace this great subject in its whole extent, and we are about to offer at least a sketch of a regular and complete theory of beauty and art. Let us begin by establishing well the method that must preside over these investigations. One can study the beautiful in two ways:--either out of us, in itself and in the objects, whatever they may be, that bear its impress; or in the mind of man, in the faculties that attain it, in the ideas or sentiments that it excites in us. Now, the true method, which must now be familiar to you, makes setting out from man to arrive at things a law for us. Therefore psychological analysis will here again be our point of departure, and the study of the state of the soul in presence of the beautiful will prepare us for that of the beautiful considered in itself and its objects. Let us interrogate the soul in the presence of beauty.