AEsthetics, regarded as the science of the Beautiful, or of the principles of art and taste, proceeds by two fundamentally distinct methods, the metaphysical or a priori, and the scientific or empirical. The first starts with assuming that beyond the material world lies some ultimate conception which is more or less embodied in different forms of beauty, and seeks by means of this conception to determine deductively what it is that constitutes beauty. The scientific method compares and classifies recognised phenomena of beauty and art, and endeavours by so doing to establish certain laws. It should be remembered, however, that most writers on aesthetics have treated the subject as part of a philosophic whole, the principles of which it is first necessary to grasp. The science of the Beautiful also includes the determination of the laws and nature of the Sublime, and the Ludicrous, and much has been written on their mutual relations, especially as regards the Ludicrous. Psychologically considered, the Beautiful is a source of pleasure which presents unity in diversity, and so is easy of apprehension. Any trait which entails conflict, or difficulty of apprehension, jars, and turns the pleasure into pain. Artistic pleasure, therefore, springs largely from harmony. Lessing lays stress on this principle in his Laokoon. "Among the ancients," he says, "beauty was the highest law of the plastic arts. And this, once proved, it is a necessary consequence that everything else over which their range could be at the same time extended, if incompatible with beauty, gave way entirely to it; if compatible was at least subordinate." The power of association in aesthetic feeling is too well known to need dilating upon, and the whole question is greatly complicated by the fact that not only the associations of the individual, but those of the race must be considered.