THE STORY OF PHILOSOPHY2 The Lives and Opinions

s8o THE STORY OF PHILOSOPHY
but in its failure to explain what is that subtle power whereby an or-
ganism is enabled to make these prophetic adjustments
that characterize
vitality. In a chapter added to later editions, Spencer was forced to^discuss
"The Dynamic Element in Life," and to admit that his definition
had not really revealed the nature of life. "We are obliged to confess that
Life in its essence cannot be conceived in terms."
physico-chemical 36 He
did not realize how damaging such an admission was to the unity and
completeness of his system.
As Spencer sees in the life of the individual an adjustment of internal
to external relations, so he sees in the life of the species a remarkable
adjustment of reproductive fertility to the conditions of its habitat. Reproduction
arises originally as a readaptation of the nutritive surface to
the nourished mass; the growth of an amoeba, for example, involves an
increase of mass much more rapid than the increase in the surface through
which the mass must get its nourishment. Division, budding, spore-formation,
and sexual reproduction have this in common, that the ratio of mass
to surface is reduced, and the nutritive balance is restored. Hence thegrowth
of the individual organism beyond a certain point is dangerous;
and normally growth gives way, after a time, to reproduction.
On the average, growth varies inversely with the rate of energy-ex-
penditure; and the rate of reproduction varies inversely with the degree
of growth.
"It is well known to breeders that if a filly
is allowed to bear a
foal, she is thereby prevented from reaching her proper size. ... As a
converse fact, castrated animals, as capons and notably cats, often become
larger than their unmutilated associates." 37 The rate of reproduction
tends to fall as the development and capability of the individual
progress. "When, from lowness of organization,
the ability to contend
with external is dangers small, there must be great fertility to compensate
for the consequent mortality; otherwise the race must die out. When,
on the contrary, high endowments give much capacity for self-preservation,
a correspondingly low degree of fertility is requisite," lest the rate
of multiplication should outrun the supply of food. 38 In general, then,
there is an opposition of individuation and genesis, or individual development
and fertility. The rule holds for groups and species more- regularly
than for individuals : the more highly developed the species or the group,
the lower will its birth-rate be. But it holds for individuals too, on the
average. For example, intellectual development seems hostile to fertility. "Where exceptional fertility exists, there is sluggishness of mind, and
where there has been, during education, excessive expenditure in mental
action, there frequently follows a complete or partial infertility. Hence
the particular kind of further evolution which Man is hereafter to undergo
is one which, more than any other, may be expected to cause a
8*
decline in his power of reproduction.*' Philosophers are notorious for
% 120. "11,459-