INTRODUCTION TO SOCIOLOGY 585
and objective evolution of social phenomena; they are there- fore natural. Thus sociology and societies are the true, logical continuation of the antecedent sciences and of the universal order.
Biology and psychology are the natural transition to social science. Biology reveals to us cellular differentiations, cellu- lar associations, that is to say, groupings and combinations of organisms; it reveals to us a physiological division of functions, in relationship with an organic differentiation contributing to the collective life and structure of the whole ; it shows to us the division of sexes which imposes, in certain species, at least a momentary union of beings who are forced by nature to com- plete one another, and also even at times to disappear when once the work of reproduction is realized.
Psychology, apart from the collective organization of all of the organs and groups of organs belonging to the nervous system, reveals to us associations of movements, of emotions, of sentiments, of ideas, of states of consciousness more or less complex, sympathetic phenomena: fears, panics, imitations, etc.
In the case of certain animals, groupings of the collective psychic states are produced by the mere fact of juxtaposition, by the placing together of individuals of the same species or of different species. We see the formation of animal societies, just as we have seen the uniting of cells and groups of cells. Thus, naturally, to the other properties of unorganized, organ- ized, and conscious matter are added the social properties, by a slow evolution which is so unbroken that even psychology seems necessarily to be collective; from which follows the deduction that even society should be a phenomenon of col- lective psychology. In fact, sociality appears at the summits of biology and psychology, which, by a truly organic filiation, are united by it to the structure of societies.
Thus, social science begins where the domain of biology and psycho-physiology ends, but there is continuity between these two domains.
Another observation results from the history of the organiza- tion of social science and as a corollary from the preceding
