The future of moral evolution is accordingly infinite, but its character is more and more determinate at every step. Mankind can never, without perishing, surrender its animal nature, its need to eat and drink, its sexual method of reproduction, its vision of nature, its faculty of speech, its arts of music, poetry, and building. Particular races cannot subsist if they renounce their savage instincts, but die, like wild animals, in captivity; and particular individuals die when not suffered any longer to retain their memories, their bodies, or even their master passions. Thus human nature survives amid a continual fluctuation of its embodiments. At every step twigs and leaves are thrown out that last but one season; but the underlying stem may have meantime grown stronger and more luxuriant. Whole branches sometimes wither, but others may continue to bloom. Spiritual unity runs, like sap, from the common root to every uttermost flower; but at each forking in the growth the branches part company, and what happens in one is no direct concern of the others. The products of one age and nation may well be unintelligible to another; the elements of humanity common to both may lie lower down. So that the highest things are communicable to the fewest persons, and yet, among these few, are the most perfectly communicable. The more elaborate and determinate a man’s heritage and genius are, the more he has in common with his next of kin, and the more he can transmit and implant in his posterity for ever. Civilisation is cumulative. The farther it goes the intenser it is, substituting articulate interests for animal fumes and for enigmatic passions. Such articulate interests can be shared; and the infinite vistas they open up can be pursued for ever with the knowledge that a work long ago begun is being perfected and that an ideal is being embodied which need never be outworn. [Sidenote: Nature and human nature.]