The authorities hold that the basic element concerned in the manifestation of the æsthetic emotional feeling is the _sensory_ element, which consists of the pleasure arising from the perception of objects of vision or hearing which are deemed beautiful. There is a certain nervous satisfaction which arises from the perception of the sensation of the sight of a beautiful thing, or of the hearing of beautiful sound. Just _why_ certain sights prove agreeable and others disagreeable, or certain sounds pleasant and others unpleasant, is very difficult to determine. Association and habit may have something to do with the beauty of sight object, and there may be natural harmony of vibration in colors as there is in sound. In the case of sounds there is undoubtedly a natural harmony between the vibrations of certain notes of the scale and inharmony between others. Some have held that the secret of the enjoyment of music is found in the natural appreciation of rhythm, as rhythm is a cosmic manifestation evident in everything from great to small. But these theories do not account for the differences existing in the tastes regarding color and music manifested by different individuals, races, and classes of people. Grant Allen says: "The vulgar are pleased with great masses of color, especially red, orange, and purple, which give their coarse, nervous organization the requisite stimulus. The refined, with nerves of less caliber, but greater discriminativeness, require delicate combinations of complementaries and prefer neutral tints to the glare of the primary hues. Children and savages love to dress in all the colors of the rainbow." In the same way persons of certain types of taste are pleased with "rag time" and cheap, rollicking songs or dances, while others shudder at these and find delight in the classic productions of the great composers. There is also the _intellectual_ element to be reckoned with in the æsthetic emotions. The intellect must discover the beauty in certain objects before the emotion is aroused by the perception. Halleck says: "Every time the mind discerns unity amid variety, order, rhythm, proportion, or symmetry, an æsthetic emotion arises. * * * The traveler with a trained intellect will see far more beauty than an ignorant one. In looking at a cathedral, a large part of the æsthetic enjoyment comes from tracing out the symmetry, from comparing part with part. Not until this process is complete will the full beauty of the structure as a whole be perceived. If the traveler knows something of mediæval architecture before starting on his European trip, he will see far more beauty. The opposite of the æsthetic, which we call the ugly, is the unsymmetrical, the disorderly--that in which we can discover no rhythm, plan, or beauty."