to its substance. The genealogy of progress
is like that of man, who can never repudiate a single ancestor. It
starts, so to speak, from a single point, free as yet to take any
direction. When once, however, evolution has taken a single step, say in
the direction of vertebrates, that step cannot be retraced without
extinction of the species. Such extinction may take place while progress
in other lines is continued. All that preceded the forking of the dead
and the living branch will be as well represented and as legitimately
continued by the surviving radiates as it could have been by the
vertebrates that are no more; but the vertebrate ideal is lost for ever,
and no more progress is possible along that line.

[Sidenote: Perfectibility.]

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
th