with the unity that will concentrate and sustain attention, and thus call forth the highest and keenest energy of intellectual activity. Hence the function of rhythm in music, poetry and oratory; of composition and perspective in painting; of design in architecture. The more perfect the relations are which constitute order, the more _clearly_ will the unity of the object _shine forth_; hence the more fully and easily will it be grasped, and the more intense the esthetic pleasure of contemplating it. St. Thomas thus sums up the objective conditions of the beautiful: _integrity_ or _perfection_, _proportion_ or _harmony_, and _clarity_ or _splendour_.(205) 56. SOME DEFINITIONS OF THE BEAUTIFUL.—An object is beautiful when its contemplation pleases us; and this takes place when the object, complete and entire in itself, possesses that order, harmony, proportion of parts, which will call forth the full and vigorous exercise of our cognitive activity. All this amounts to saying that the beauty of a thing is the _revelation or manifestation of its natural perfection_.(206) Perfection is thus the _foundation_ of beauty; the showing forth of this perfection is what constitutes beauty _formally_. Every real being has a nature which constitutes it, and activities whereby it tends to realize the purpose of its existence. Now the perfection of any nature is manifested by the proportion of its constitutive parts and by the harmony of all its activities. Hence we see that order is essential to beauty because order shows forth the perfection of the beautiful. An object is beautiful in the degree in which the proportion of its parts and the harmony of its activities show forth the perfection of its nature. Thus, starting with the subjective, _a posteriori_ definition of beauty from its effect: _beauty is that whose contemplation pleases us_—we have passed to the objective and natural definition of beauty by its properties: _beauty is the evident integrity, order, proportion and harmony, of an object_—and thence to what we may call the _a priori_ or synthetic definition, which emphasizes the perfection revealed by the static and dynamic order of the thing: _the beauty of an object is the manifestation of its natural perfection by the proportion of its parts and the harmony of its activities_.(207)