This answers for the department of physics and physiology. We will let Guizot, the historian, speak for the political and social realm: 'All things, at their origin, are nearly confounded in one and the same physiognomy; it is only in their aftergrowth that their variety shows itself. Then begins a new development which urges forward societies toward that free and lofty unity, the glorious object of the efforts and wishes of mankind.'
We find an illustration of this law in the simplest of the sciences, if the nebular hypothesis be true, as most astronomers believe. We have first the chaotic, nebulous matter, then the formation of worlds therefrom, by a continuous process of unfolding. Each world is a unit within itself, but part of a still greater unit composed of a system of worlds revolving around the same sun; and this greater unit, part of one which is still greater—a star cluster, composed of many planetary systems, and subject to the same great cosmical laws. If the theory be correct, we find, in this example, the heterogeneous derived from the simple, and far more completely an organized unit, with all its complexity, than was the chaotic mass from which development originally proceeded.
We find additional illustration in coming to our own world. Its primeval geography was simple and uniform; there was little diversity of coast line, soil, or surface. But the cooling process of the earth went on, the surface contracted and ridged up, the exposed rocks were disintegrated by the action of the atmosphere and the waters; the sediment deposited in the bottom of the seas was thrown to the surface; continents were enlarged, higher mountain ranges upheaved, the coasts worn into greater irregularity of outline; and everywhere the soil became more composite, the surface more uneven, the landscape more variegated.
Corresponding changes have taken place in the climate. At first the temperature of the earth was much warmer than now, and uniform in all parallels of latitude, as is shown by the fossil remains. Now we have a great diversity of climate, whether we contrast the polar with the torrid regions, or the different seasons of the temperate zone with each other.
The same law of increasing diversity obtains in the fauna and flora of the various periods of geological history. The earliest fossil record of animal life is witness to the simplicity of organic structure. Among vertebrated animals, fishes first appear, next reptiles, then birds; still higher, the lower type of animals which suckle their young; and as the strata become more recent, still higher forms of mammalia, till we reach the upper tertiary, in which geologists have discovered the remains of many animals of complex structure nearly allied to those which are now in existence. In the historic period appear many organic forms of still greater complexity, with man at the head of the zoological series.
In this glance of zoological progress, we discover increasing complication of two kinds; for while the individual structure has been constantly becoming more complex, there are now in existence the analogues of the lowest fossil types, which, with the highest, and with all the intermediate, present a maze and vastness of complication, which, in comparison with the homogeneity of the aggregate of early structure, is sufficiently obvious and impressive.
There is in this view, still another outline of increasing complexity. At first the same types prevailed all over the earth's surface; but as the soil, atmosphere, and climate changed, and the animal structure became more complex and varied, the limits of particular species became more and more localized, till the earth's surface presented zoological districts, with the fauna of each peculiar to itself.
But, what of unitization? Here, there appears to be divergence only, and that continually increasing.
Guyot says that 'the unity reappears with the creation of man, who combines in his physical nature all the perfections of the animal, and who is the end of all this long progression of organized beings.' Agassiz recognizes man alone as cosmopolite; and Comte regards him as the supreme head of the economy of nature, and representative of the fundamental unity of the anatomical scale.
But another and more obvious example of unitization in complexity, is derivable from the consideration of the animal organism, and will soon be given.