n is the dominant faculty in man,
it must perceive the lines along which he is to conform. Truth,
right, and duty must be his watchwords. These are to be the rules
and motives of all his actions. He cannot live for the body, but for
something higher, the mind. This was proven before man appeared on
the globe. He is to be a mental, intelligent being. But he is not to
be governed by appetite or mere prudential considerations. These are
animal, not human motives. These are not to be disregarded any more
than digestion can be safely disregarded by man. But they are not to
be his chief motives. He must subordinate these to the higher
motives furnished by right and duty. Man is not merely a mental but
a moral being. If he sinks below this plane of life he is not
following the path marked out for him in all his past development.
In order to progress, the higher vertebrate had to subordinate
everything to mental development. In order to become man it had to
develop the rational intelligence. In order to become higher man,
present man must subordinate everything to moral development. This
is the great law of animal and human development clearly revealed in
the sequence of physical and mental functions.

Must man be a religious being also? This question we must try to
answer in a future lecture.

CHAPTER VI

NATURAL SELECTION AND ENVIRONMENT

I have attempted to show that animal development has not been an
aimless drifting. Functions developed and organs arose and were
perfected in a certain order. First the purely vegetative organs
appeared, and the animal lived for digestion and reproduction; then
came muscle and it brought with it nerve. But these were not enough;
the brain had all the time been gradually improving, and now it
becomes the dominant function to which all others are subordinated.
The experiment was fairly tried. Mere digestion and reproduction are
carried to about the highest perfection which can be expected of
them in worms and mollusks. The bird tried what could be done with
digestion ministering to locomotion guided by the very keenest
sense-organs and controlled by no mean brain. Even this experiment
was not a success. But one organ remained, the brain, and on its
mental possibilities depend the future of the animal kingdom.
Vegetative organs and muscle have been tried and found wanting.[1]

[Footnote 1: See chart, p. 310.]

We have followed hastily the development of mind. The mind began it