In the book, he uses the term "fitness" in applying his ideas of Lamarckian evolution to society, saying for example that "It is clear that any being whose constitution is to be moulded into fitness for new conditions of existence must be placed under those conditions. Or, putting the proposition specifically—it is clear that man can become adapted to the social state, only by being retained in the social state. This granted, it follows that as man has been, and is still, deficient in those feelings which, by dictating just conduct, prevent the perpetual antagonism of individuals and their consequent disunion, some artificial agency is required by which their union may be maintained. Only by the process of adaptation itself can be produced that character which makes social equilibrium spontaneous."