THE PRINCIPLES OF BIOLOGY. 
49 
and definiteness, or both. Functional Evolution may consist 
in more actions, greater varieties of actions, or both, resulting 
in more complete co-ordination of actions, in other words, 
“ an advance towards completion of that continuous adjust¬ 
ment of internal to external relations which constitutes life.” 
Mr. Spencer pauses here to enquire in what particular 
way the higher life may manifest itself. He considers that 
it will probably not show itself in any considerable degree in 
strength or in agility, though it may to some extent in 
mechanical skill, but that it will most likely manifest itself 
in intelligence, for which there is ample room for advance, 
and in morality. There will be greater exertion of the will 
to do what our intelligence tells us we ought to do. In short, 
this more perfect co-ordination of actions is likely to take 
mainly the direction of a higher intellectual and emotional 
development. 
This conclusion is strengthened by an enquiry into the 
causes which are to bring about such results. Evolution is 
never spontaneous ; all modifications, structural or functional, 
must depend on surrounding conditions. What are the 
changes in the environment to which the human organism 
has been adjusting and will continue to adjust itself? How, 
too, do they necessitate a higher condition of the organism? 
While danger of death from predatory animals and from 
tribal combinations lessens as men grow more numerous, 
that from deficiency of food increases. Growth of population 
is therefore a permanent cause of modification to which 
civilised men are exposed. This constant increase of 
population beyond the means of subsistence stimulates the 
gradual growth of skill, intelligence, and self-control. 
Without this pressure of competition there would be no 
necessity for more thought and energy to be applied to the 
business of life, and growth of mental power would cease. 
Nothing but necessity could induce men to submit to the 
discipline of labour and self-denial, and nothing but this 
discipline could produce a continued progression. Nature, in 
fact, secures each step by a succession of trials; all mankind 
subject themselves more or less to the discipline, but all do 
not advance under it, and only those survive who do progress, 
while those who are not so stimulated to greater activity are 
on the way to extinction, as recently exemplified in the case 
of Ireland. Premature death operates in the same direction, 
for “ natural selection” causes the fittest to survive. In this 
way there is a constant progress towards higher skill, 
intelligence, and self-regulation, better co-ordination of 
actions—a more complete life. 
