14 ‘THE SHADOW OF THE WORLD'S FUTURE
or not, except as they directly affect his food-supply.
That we are partly dependent thereon is of course
self-evident. But we are only beginning to study
the physical conditions of our earth. It is already
felt that the future of climatology is subject to a
better knowledge of the energies which reach us from
space.
As regards the psychical factors which play their
part in Man’s increase, it is perhaps fairly correct
to assume that his ¢mtrimsic character to-day is not
sensibly different from what it was, say, 10,000 years
ago. Particular manifestations of human nature vary,
but so far as history throws any light upon the subject,
it does not appear that man’s real character has changed
materially. = Whether the procreative urge is unchanging
 or not, we cannot say. The complex interests
of modern life may perhaps affect it.
A study of Man’s relatively rapid numerical growth
recently shows that it is doubtless due to his accessions
 of knowledge, particularly those occurring during
the nineteenth century. The earth is richer than he
knew; his power to do what he desires is greater. He
has learnt that quite recondite ideas are of practical
value. Applied to the field of what he has discovered
in regard to Nature, it has taught him that she is
niggardly, often simply because he is ignorant. As
a fact his increased knowledge has enabled him to
exploit more successfully his complex environment.
Much of what he formerly regarded as waste turns
out to be of considerable value. Already this has
borne fruit in enabling him to live a richer life; and a
greater number can enjoy this life than ever before.
The accumulations of knowledge are potentially stores
of material wealth. We do not of course know the
limit of this development. Naturally Man’s faith in
the possibilities of his earth have become vastly greater,
and the more sanguine spirits among those versed in