What, then, is the nature of this emotional appeal which surpasses so much in intimacy, pleasure, and power the appeal to the intellect?  It is the keystone of the inward nature, that which binds all together in the arch of life.  Emotion has some ground, some incitement which calls it forth; and it responds with most energy to beauty.  In the strictest sense beauty is a unity of relations of coexistence in coloured space and appeals to the eye; it is in space what plot is in time.  Like plot, it is deeply engaged in the outward world; it exists in the sensuous order, and it shadows forth the spiritual order in man only in so far as a fair soul makes the body beautiful, as Spenser thought,—­the mood, the act, and the habit of heroism, love, and the like nobilities of man, giving grace to form, feature, and attitude.  It is primarily an outward thing, as emotion, which is a phase of personality, is an inward thing; what the necessary sequence of events, the chain of causation, is to plot,—­its cardinal idea,—­that the necessary harmony of parts, the chime of line and colour, is to beauty; thus beauty is as inevitable as fate, as structurally planted in the form and colour of the universe as fate is in its temporal movement.  And as plot has its characteristic unity in the impersonal order of God’s will, shown in time’s event, so beauty has its characteristic unity in the same order shown in the visible creation of space.  It is true that all phenomena are perceived by the mind, and are conditioned, as is said, by human modes of perception; but within the limits of the relativity of all our knowledge, beauty is initially a sensuous, not a spiritual, thing, and though the structure of the human eye arranges the harmonies of line and colour, it is no more than as the form of human thought arranges cause and effect and other primary relations in things; beauty does not in becoming humanly known cease to be known as a thing external, independent of our will, and imposed on us from without.  It is this outward reality, the harmony of sense, that sculpture and painting add in their types to the interpretation they otherwise give of personality, and often in them this physical element is predominant; and in the purely decorative arts it may be exclusive.  In landscape, which is in the realm of beauty, personality altogether disappears, unless, indeed, nature be interpreted in the mood of the Psalmist as declaring its Creator; for the reflection which the presence of man may cast upon nature as his shadow is not expressive of any true personality there abiding, but enters into the scene as the face of Narcissus into the brook.  The pleasure which the mind takes in beauty is only a part of its general delight in order of any sort; and visible artistic form as abstracted from the world of space is merely a species of organic form and is included in it.