THE BASIS OF SOCIAL SOLIDARITY 821
gest what is characteristic of instinct as such; this may be explained under certain headings as follows.
a) In the first place, the endowment involved in this sort of association is instinctive: it is physically inherited by individual animals. The tendency to live together and to pursue certain habits of life in common is in fact native. The instincts of the individuals are so correlated with each other that each without the other or others is incomplete and ineffective. The family instincts of animals are examples of this; and the maternal, sexual, racial, instinctive tendencies in man.
An important corollary is seen in the fact that such habits of life do not have to he learned. For such activities, no training is necessary, no learning from experience. This means that in such apparently co-operative actions, psychological factors are not primarily or largely involved.
h) Again, we find that, being thus stereotyped by heredity, such modes of action are fixed and unprogressive; they admit of very little modification and development. When the requisite environmental conditions are present, their working is effective and sufficient; but when the conditions change, and any degree of accommodation or readjustment is called for, the animals so endowed are more or less helpless. They are not able to substitute intelligent action for instinctive reaction.
c) Such modes of action, being in the main physically in- herited, are in their origin the product of biological laws. They have been reduced in the process of evolution to the condition of nervous functions ; they have become part of the creature's physio- logical endowment. They illustrate racial habit and selection.'* We may say, then, that such instinctive actions, however psycho- logical their results may appear to be, are in their modus operandi biological reactions. They can be explained only on the bio-
- That is they have arisen as other instincts have, by natural selection
working upon advantageous variations, both physical and mental. For detailed discussions of the theories of the origin of instinct the reader may consult my work Development and Evolution, and also the little book already referred to called Darwinism and the Humanities. Important works on the subject which have some reference to the social instincts are Lloyd Morgan's Habit and Instinct, and K. Groos's The Play of Animals and The Play of Man,
