THE BASIS OF SOCIAL SOLIDARITY 823
proceed by trial and error, persistent imitation, gradual selection of happy hits in the direction of better accommodation and ad- justment. In this they stand out in striking contrast to the in- stinctive acts already described. Their points of distinction are in the main the following.
a) These acquired modes of collective action illustrate social transmission rather than physical heredity. The great body of the animals' collective activities are re-established in each genera- tion, being transmitted from old to young by processes of imita- tive absorption. There is, indeed, in the actions handed down in this way, a real continuity from generation to generation ; a "social heredity," as it has been called, as effective and compell- ing as physical heredity. But it is maintained by actual learning, on the part of countless individuals, who are in this sense — and must be — sufficiently "plastic" to absorb the lessons of the family and group tradition. Each must be plastic in the presence of the group life and its agencies.
Now it is evident that such learning, with the resulting form- ing or molding effect upon individuals, is in sharp contrast to the sort of activity described above as instinctive and biological. In order to be plastic, the individual must be relatively free from the compulsion of inherited instinct. The modification of func- tion and structure involved in effective learning requires the relative decay of fixed reactions; greater relative plasticity of nerve and muscle takes its place.
h) So far as the individual is concerned, this sort of plastic activity, with the resulting association of individuals together, allows essential growth and progress and in fact issues in it. The individual grows into the tradition of the group, just as, in other cases, by instinctive acts, the individual shows himself already possessed of the hereditary traits of the race. But from the point of view of the group, this plastic learning is an agency of con- formity, conservation, stability, and solidarity. The individual does not go beyond what the group life has already acquired : his learning is limited to tradition. All the individuals of the group learn the same things; and what they learn is the body of useful actions already established in the collective life of the group.
