change from homogeneity to heterogeneity. To Mr. Spencer must be assigned the honor of having demonstrated that integration, or the change from indefiniteness to definiteness of structure, is an equally vital part of the process.

Now the advance from indefinite homogeneity to definite heterogeneity in structure and function, which constitutes organic development, has been found to be equally the chief characteristic of social progress. On considering primitive societies, we find them affected by no causes of heterogeneity, except those resulting from the establishment of the various family relationships. As Mr. Maine has shown, in early times the family and not the individual was the social unit. In the absence of anything like national or even civic organization, each family chief was a monarch in miniature, uniting in his own person the functions of king, priest, judge, and parliament; yet he was no less a digger and hewer than his subject children, wives, and brethren. Commercially, it is needless to state, all primitive communities are homogeneous. In any barbarous tribe the number of different employments is very limited, and such as there are admit of being undertaken indiscriminately by any one. Every man is his own butcher and baker, his own tailor and carpenter, his own smith, and his own weapon-maker. Now the progress of such a society toward a civilized condition begins with the differentiation and integration of productive occupations. That each specialization of labor entails increased efficiency of production, which reacting brings out still greater specialization, is known to the tyro in political economy. Nor is it less obvious that, with the advance of civilization, labor has been steadily increasing in heterogeneity, not only with regard to its division among different sets of laborers, but also with regard to its processes, and even its instruments. The distinguishing characteristic of modern machinery, as compared with the rude tools of the Middle Ages or the clumsy apparatus of the ancients, is its heterogeneity. The contrast between the steam-engine of to-day and the pulleys, screws, and levers of a thousand years ago assures us that the growing complexity of the objects which labor aims at is paralleled by the growing complexity of the modes of attaining them. Turning to government, we see that by differentiation

in the primeval community some families acquired supreme power, while others sank, though in different degrees, to the rank of subjects. The integration of allied families into tribes, and of adjacent tribes into nations, as well as that kind of integration exhibited at a later date in the closely knit diplomatic interrelations of different countries, are marked steps in social progress. Next may be mentioned the differentiation of the governing power into the civil and the ecclesiastical; while by the side of these ceremonial government grows up insensibly as a third power, regulating the minor details of social intercourse none the less potently because not embodied in statutes and edicts. Comparing the priests and augurs of antiquity with the dignitaries of the medieval Church, the much greater heterogeneity of the latter system becomes manifest. Civil government likewise has become differentiated into executive, legislative, and judicial. Executive government has been divided into many branches, and diversely in different nations. A comparison of the Athenian popular government with the representative systems of the present day shows that the legislative function has no more than any of the others preserved its origi nal homogeneity. While the contrast between the Aula Regis of the Norman kings and the courts of common law, equity, and admiralty,-county courts, queen's courts, State courts, and Federal courts, which are lineally descended from it, tells us the same story concerning the judicial power. Nor should it be forgotten that the steady expansion of legal systems, to meet the exigencies which civilization renders daily more complex, is an advance from homogeneity to heterogeneity.

Not only is the general law of organic development thus illustrated in the internal progress of all nations, it is also conspicuously exemplified in the divergent courses pursued by many communities which have started from a common origin. The Germanic tribes, which in the fifth and sixth centuries acquired control over Roman Europe, were nearly homogeneous with respect to each other. The description of the Germans, left by Tacitus, would doubtless have applied indiscriminately to Goths, Saxons, Franks, and Lombards. None of them had advanced far beyond the primitive patriarchal system of gov ernment, nor had any of them experienced much industrial

differentiation; and so there was but little scope left them for the display of social unlikenesses. Even so late as the twelfth century, the interior structure of each great European community was, except in minor points of detail, very similar to that of all the others. The feudal system, chivalry, the crusading spirit, scholasticism, monasticism, serfdom, baronial isolation, private war, ecclesiastical supremacy, these were the striking features of society at that time, in England as well as in Spain, in France as well as in Italy. But in our day the heterogeneity is notable. The so-called Anglo-Saxon nations are differentiated from all the rest by their political individualism; but the free organization of America differs widely also from the free organization of England. Absolutism, on the other hand, is not the same thing in Austria that it is in France, nor is Catholicism the same thing in France that it is in Spain; while the free Protestantism of Prussia bears little resemblance to the narrow Protestantism of Scotland and Sweden.

Whether the human race, ethnologically considered, has ever presented a close approach to homogeneity, is perhaps uncertain. For our present purpose, however, it is immaterial whether the various races of mankind are descended from one primitive stock or from several primitive stocks. It is enough to show that where there has been marked social progress there has also been marked ethnic differentiation. The widely spread tribes of unprogressive American Indians, now so rapidly disappearing, have retained to the end their ancient physical, intellectual, and moral homogeneity. But in the descendants of the primitive Indo-Europeans, from the flabby and pursy Hindu to the wiry and long-limbed Kentuckian, may be seen the immense heterogeneity entailed by long-continued differences of social organization and of physical environment. They present numberless unlikenesses of size, strength, complexion, feature, of anatomical conformation, of moral susceptibility, and of intellectual capacity. Still further illustration is to be found in the languages spoken by these Aryan nations. Eight families of languages, containing each from half a dozen to a score of mutually unintelligible dialects, are descended from the common mother tongue spoken by our Aryan ancestors before they had left the neighborhood of the Hindu Kush. The development

of the Semitic languages from a single parent tongue furnishes a parallel example. But this is far from being the whole of the case, for a careful study of the structure of language in itself shows that its growth takes place by differentiation and integration. I have elsewhere* collected some evidence of this; proving, among other things, that integration takes place in the progressive coalescence of roots with their terminations, as well as in the concentration of syllabic sounds, and in the increasing logical coherence of clauses; while the generation of dialects, the rise of parts of speech, the growth of widely divergent words from a common root, as well as the growth of widely divergent languages from a common stock, were shown to be prominent instances of differentiation.

But, by a still greater sweep of generalization, Mr. Spencer has likewise included in Von Baer's formula the changes of inorganic nature, having traced the development which it describes throughout a vast number of phenomena, both telluric and cosmic.† Thus, by reason of its very comprehensiveness, the law of universal evolution can no longer supply the precise kind of information we desire regarding historic phenomena. It is the law not only of social changes but of all other changes. It utters no truth concerning human development which is not true of all development. Though it is the ultimate law of history, it is silent respecting the differential characteristic by which a historic event is distinguished from a physical event. The ultimate and general formula needs to be supplemented by one that is derivative and special; which shall describe organic evolution in terms. inapplicable to inorganic phenomena; which shall be, in short, a comprehensive definition of life. This additional step was taken by Mr. Spencer, in 1855. In his "Principles of Psychology," published in that year, is to be found the first statement of that "proximate definition of life,” which contains by implication the law of organic as distinguished from inorganic progress.‡

* "The Evolution of Language," North American Review, October, 1863. + First Principles (2d ed.), pp. 308–396.

As a formula for social progress, it had already been foreshadowed, though probably without full consciousness of its entire significance, in Mr. Spencer's Social Statics, published four years earlier.

According to this exhaustive definition, life- and intelligence likewise, as the highest known manifestation of lifeconsists in the continuous establishment of relations within the organism in correspondence with relations already existing in the environment. The degree of life is high or low according as the correspondence between internal and external relations is complex or simple, extensive or limited, complete or partial, perfect or imperfect. The lowest forms of life respond only to the simpler and more homogeneous changes which af fect the whole of their surrounding medium. The relations established within a plant answer only to the presence or absence of a certain quantity of light and heat, and to the chemical and hygrometric relations existing in the enveloping atmosphere and subjacent soil. In a zoophyte, besides general relations similar to these there is established a special relation in correspondence with the external existence of certain mechanical irritants, so that its tentacles contract on being touched. The increased number of correspondences, as we ascend the animal scale, may be seen by contrasting the polyp, which can simply distinguish between soluble and insoluble matters, or between opacity and translucence in its environment, with the keen-scented bloodhound and the far-sighted vulture. And the increase of complexity may be appreciated by comparing the motions respectively gone through by the polyp on the one hand, and by the dog or vulture on the other, while securing and disposing of its prey. The advance to higher forms of life consists in the orderly establishment of internal relations of sequence answering to external relations of coexistence and sequence, that are continually more heterogeneous, more remote in space and in time, and at once more general and more special; until at last we reach civilized man, whose intelligence responds to every variety of external stimulus, whose most ordinary needs are supplied by apparatus of amazing complexity, and whose mental sequences are often determined by circumstances as distant as the Milky Way, and as ancient as the birth of the solar system.

The lower forms of life respond to the changes going on about them only in an imperfect and general way. A tree, for instance, meeting by changes within itself none but physical