Homans had come to the view that theory should be expressed as a deductive system, in this respect falling under the influence of the logical empiricist philosophers of that period. Substantively, he argued that a satisfactory explanation in the social sciences is based upon "propositions"—principles—about individual behavior that are drawn from the behavioral psychology of the time. Homans didn't believe that new propositions are needed to explain social behavior. The laws of individual behavior developed by Skinner in his study of pigeons explain social behavior as long as we take into account the complications of mutual reinforcement.