486 THE AMERICAN JOURNAL OF SOCIOLOGY
view until, in the last of these points of view, the biological factor appeared and then the psychic factor in particular, the last of which completed the series of sciences whose co-ordination, not isolated, but encyclopaedic, is at the basis of sociology. Now, it is only after these divers interpretations, at first exclusive, but later more and more combined, that, following the principle of Poinsot, we shall be able in time to begin to study societies in themselves as phenomena in part distinct from antecedent phenomena, although they are but the more complicated con- tinuation of the same.
As in mechanics we call the causes of movement forces, with- out inquiring into the nature of these causes, in the same way we call the causes of social movement social forces. There are social forces as there were before them vital, physical, chemical, and astronomical forces.
The general problem of rational mechanics is to determine the effect of different forces acting simultaneously upon a given body, the separate effect of each of the forces being known. Mechanics is, then, the science of the combinations of forces. So long as social science was in the domain of empiricism, and so long as statesmen were able to imagine that they were the mechanicians of the societies whose forces they combined in view of certain results, the mechanical conception lent itself admirably to their illusion ; besides, it was a first step toward truth. In politics, as in mechanics, it was observed that the meeting of forces may result either in their reciprocal neutrali- zation, the consequence of which is repose, equilibrium, or else in movement. Mechanical science and political art had, there- fore, this object in common : the investigation of the conditions or circumstances of equilibrium and of movement ; the only difference was in the nature of the bodies constituting the sub- ject of research.
The definition of forces implies the law of inertia ; a body remains in repose so long as no exterior force acts upon it ; or, if it is in motion and no new force intervenes, its movement will be uniform and in a straight line. The statesmen applied this law of inertia by isolating their peoples, by protecting them as
