Man is so educable an animal that it is difficult to distinguish between that part of his character which has been acquired through education and circumstance, and that which was in the original grain of his constitution. His character is exceedingly complex, even in members of the simplest and purest savage race; much more is it so in civilised races, who have long since been exempted from the full rigour of natural selection, and have become more mongrel in their breed than any other animal on the face of the earth. Different aspects of the multifarious character of man respond to different calls from without, so that the same individual, and, much more, the same race, may behave very differently at different epochs. There may have been no fundamental change of character, but a different phase or mood of it may have been evoked by special circumstances, or those persons in whom that mood is naturally dominant may through some accident have the opportunity of acting for the time as representatives of the race. The same nation may be seized by a military fervour at one period, and by a commercial one at another; they may be humbly submissive to a monarch, or become outrageous republicans. The love of art, gaiety, adventure, science, religion may be severally paramount at different times.

One of the most notable changes that can come over a nation is from a state corresponding to that of our past dark ages into one like that of the Renaissance. In the first case the minds of men are wholly taken up with routine work, and in copying what their predecessors have done; they degrade into servile imitators and submissive slaves to the past. In the second case, some circumstance or idea has finally discredited the authorities that impeded intellectual growth, and has unexpectedly revealed new possibilities. Then the mind of the nation is set free, a direction of research is given to it, and all the exploratory and hunting instincts are awakened. These sudden eras of great intellectual progress cannot be due to any alteration in the natural faculties of the race, because there has not been time for that, but to their being directed in productive channels. Most of the leisure of the men of every nation is spent in rounds of reiterated actions; if it could be spent in continuous advance along new lines of research in unexplored regions, vast progress would be sure to be made. It has been the privilege of this generation to have had fresh fields of research pointed out to them by Darwin, and to have undergone a new intellectual birth under the inspiration of his fertile genius.

A pure love of change, acting according to some law of contrast as yet imperfectly understood, especially characterises civilised man. After a long continuance of one mood he wants to throw himself into another for the pleasure of setting faculties into action that have been long disused, but not yet paralysed by disuse, and which have become fidgety for employment. He has so many opportunities for procuring change, and has so complex a nature that he easily learns to neglect a more deeply-seated feeling that innovation is wicked, and which is manifest in children and barbarians. To a civilised man the varied interests of civilisation are temptations in as many directions; changes in dress and appliances of all kinds are comparatively inexpensive to him owing to the cheapness of manufactures and their variety; change of scene is easy from the conveniences of locomotion. But a barbarian has none of these facilities: his interests are few; his dress, such as it is, is intended to stand the wear and tear of years, and all weathers; it is relatively very costly, and is an investment, one may say, of his capital rather than of his income; the invention of his people is sluggish, and their arts are few, consequently he is perforce taught to be conservative, his ideas are fixed, and he becomes scandalised even at the suggestion of change.

The difficulty of indulging in variety is incomparably greater among the rest of the animal world. If a pea-hen should take it into her head that bars would be prettier than eyes in the tail of her spouse, she could not possibly get what she wanted. It would require hundreds of generations in which the pea-hens generally concurred in the same view before sexual selection could effect the desired alteration. The feminine delight of indulging her caprice in matters of ornament is a luxury denied to the females of the brute world, and the law that rules changes in taste, if studied at all, can only be ascertained by observing the alternations of fashion in civilised communities.

There are long sequences of changes in character, which, like the tunes of a musical snuff-box, are regulated by internal mechanism. They are such as those of Shakespeare's "Seven Ages," and others due to the progress of various diseases. The lives of birds are characterised by long chains of these periodic sequences. They are mostly mute in winter, after that they begin to sing; some species are seized in the early part of the year with so strong a passion for migrating that if confined in a cage they will beat themselves to death against its bars; then follow courtship and pairing, accompanied by an access of ferocity among the males and severe fighting for the females. Next an impulse seizes them to build nests, then a desire for incubation, then one for the feeding of their young. After this a newly-arisen tendency to gregariousness groups them into large flocks, and finally they fly away to the place whence they came, goaded by a similar instinct to that which drove them forth a few months previously. These remarkable changes are mainly due to the conditions of their natures, because they persist with more or less regularity under altered circumstances. Nevertheless, they are not wholly independent of circumstance, because the period of migration, though nearly coincident in successive years, is modified to some small extent by the weather and condition of the particular year.

The interaction of nature and circumstance is very close, and it is impossible to separate them with precision. Nurture acts before birth, during every stage of embryonic and pre-embryonic existence, causing the potential faculties at the time of birth to be in some degree the effect of nurture. We need not, however, be hypercritical about distinctions; we know that the bulk of the respective provinces of nature and nurture are totally different, although the frontier between them may be uncertain, and we are perfectly justified in attempting to appraise their relative importance.

I shall begin with describing some of the principal influences that may safely be ascribed to education or other circumstances, all of which I include under the comprehensive term of Nurture.