ng intensity, the members of his clan,
tribe, and nation. These become, psychologically speaking, a portion
of himself, and stand with him against the world at large. From
the standpoint here outlined, prejudice or its analogue is the
starting-point, and our question becomes one of the determination of
the steps of the process by which man mentally allied with himself
certain portions of his environment to the exclusion of others.

If we look for an explanation of the hostility which a group feels
for another group, and of the sympathy which its members feel for one
another, we may first of all inquire whether there are any conditions
arising in the course of the biological development of a species
which, aside from social activities, lead to a predilection for those
of one's own kind and a prejudice against different groups. And we do,
in fact, find such conditions. The earliest movements of animal life
involve, in the rejection of stimulations vitally bad, an attitude
which is the analogue of prejudice. On the principle of chemiotaxis,
the micro-organism will approach a particle of food placed in the
water and shun a particle of poison; and its movements are similarly
controlled by heat, light, electricity, and other tropic forces.[159]
The development of animal life from this point upward consists in
the growth of structure and organs of sense adapted to discriminate
between different stimulations, to choose between the beneficial and
prejudicial, and to obtain in this way a more complete control of the
environment. Passing over the lower forms of animal life, we find in
the human type the power of attention, memory, and comparison highly
developed, so that an estimate is put on stimulations and situations
correspondent with the bearing of stimulations or situations of this
type on welfare in the past. The choice and rejection involved in this
process are accompanied by organic changes (felt as emotions) designed
to assist in the action which follows a decision.[160] Both the
judgment and the emotions are thus involved in the presentation to the
senses of a situation or object involving possible advantage or hurt,
pleasure or pain. It consequently transpires that the feelings called
out on the presentation of disagreeable objects and their contrary
are very different, and there arise in this connection fixed mental
attitudes corresponding with fixed or habitually recurrent external
situations--hate and love, prejudic