We have the unity of separate things subjected to one and the same influence, as the unity of clouds as they are driven by parallel winds, or ordered by electric currents: there is the unity of myriads of sea waves, of the bending and undulating of forest masses.
In creatures capable of will, there would be the unity of acts controlled, in all their apparent variety, by its directing power; and the unity of emotions in the masses, when swayed by some common impulse.
There is also the unity of the origin of things arising from one source, always suggesting their common brotherhood: in matter this is manifested in the unity of the branches of the trees, of the petals and starry rays of flowers, of the beams of light, of heat, &c., &c.; in spiritual creatures it is their filial relation to Him from whom they have their being.
There is the unity of sequence, which is that of things which form links in chains, steps in ascent, and stages in journeys; this, in matter, is the unity of communicable forces in their continuance and propagation from one thing to another; it is the passing upward and downward of beneficent effects among all things; it is the melody of sounds; the beauty of continuous lines; and orderly successions of motions and times. In spiritual creatures, it is their own constant building up by true knowledge and consecutive efforts to higher perfection, and the singleness and straightforwardness of their tendencies to more complete union with God.
There is the unity of membership, which is the union of things separately imperfect into a perfect whole; this is the great unity of which all other unities are but parts and means. In matter it is the consistency of bodies, the harmony of sounds;—with spiritual beings, it is their love, happiness, and life in God. But this unity cannot subsist between things similar to each other. Two or more equal or like things cannot be members the one of the other, nor can they form one or a whole thing. Two they must remain both in nature and in our conception unless they are united by a third. Thus the arms, which are like each other, remain always two arms in our conception, and could not be united by a third arm, but must be linked by something which is not an arm, and which, imperfect without them as they without it, will, with them, form one perfect body. Nor is unity even thus accomplished without a difference and opposition of direction in the setting on of members. Therefore, among things which are to have membership with each other, there must be difference or variety; and though it is possible that many like things may be made members of one body, yet it is very remarkable that this stricture appears rather characteristic of the lower creatures than the higher, as the many legs of the caterpillar, and the arms and suckers of Radiata seem to prove. As we rise in the order of being the number of similar members becomes less; their structure appearing based on the principle of two things united by a third;—a constant type even in matter of the Triune Existence.
Out of the necessity of unity arises that of variety, a necessity vividly felt, because it lies at the surface of things, and is assisted by our love of change and the power of contrast. It were a mistake to suppose that mere variety, without a linking principle of unity, is, necessarily, either agreeable or beautiful.
'All are needed by each one,
Nothing is fair or good alone.
I thought the sparrow's note from heaven,
Singing at dawn on the alder bough;
I brought him home in his nest at even;
He sings the song, but it pleases not now,
For I could not bring home the river and sky;—
He sang to my ear,—they sang to my eye.
The delicate shells lay on the shore;
The bubbles of the latest wave
Fresh pearls to their enamel gave;
And the bellowing of the savage sea
Greeted their safe escape to me.
I wiped away the weeds and foam,
I fetched my seaborn treasures home;
But the poor, unsightly, noisome things
Had left their beauty on the shore
With the sun, and the sand, and the wild uproar.'
It is not mere unrelated variety which charms us, for a forest of all manner of trees is poor in its effect, while a mass of one species of trees is sublime;—the swan, with its purity of unbroken whiteness, is one of the most beautiful of creatures. It is, indeed, only harmonious and chordal variety, that variety which is necessary to secure and extend unity (for the greater the number of objects which by their differences become members of one another, the more extended and sublime is their unity), which is essentially beautiful. Variety is never so conspicuous as when united with some intimation of unity. For example, the perpetual change of clouds is monotonous in its very dissimilarity, nor is difference ever striking where no connection is implied; but if through a range of barred clouds crossing half the heavens, all governed by the same forces, and falling into one general form, there be yet a marked and evident dissimilarity between each member of the great mass—one more finely drawn, the next more delicately moulded, the next more gracefully bent—each broken into differently modelled and variously numbered groups,—the variety is doubly striking because contrasted with the perfect unity and symmetry of which it forms a part.
Now, of that which is thus necessary to the perfection of things, all types and suggestions must be beautiful in whatever way they may suggest or manifest it. To the perfection of beauty in lines, colors, forms, masses, or multitudes, the appearance of unity is absolutely essential. Let the artist look to it, that our pictures may gain expression; our music cease to weary us through the unceasing dissimilarity of its parts, highly adorned arabesques running into each other, graceful, but without significance, without any perceptible principle of unity in the jarring 'motifs;' and our poems have some certain theme, that their highly wrought details may not confuse and bewilder the spirit always in search of some central unity. Like the burning sands which, clinging not together in any sweet union of fellowship, blind and confuse us with their drifting masses, are all such essays in art; for an idea capable of quickening an artistic creation must be vitally One, and every great work, notwithstanding its variety and the manifold complexity of its parts, must form a Whole.
The association of ideas, upon which is based the unity of the continuous life of the individual, with the pervading sense of personal identity, has been aptly called the 'cohesion of the moral world.' It is not less powerful, less irresistible, than that of the physical world. The association of ideas is a constituent and necessary phase of the unity of our mental and moral being, the indispensable condition of all development, whether of mind or soul. Without the power of association, the intellect would strive in vain to construct consecutive trains of thought; it would indeed be condemned to eternal infancy, because, as it ascertained new relations, those already acquired would escape, and a labor constantly renewed would be requisite to regain them. Without association of ideas, no voluntary virtue would be possible; and at the end of long years of effort and self-restraint, we would have gained no additional control over the course of our impetuous passions.