Sociology studies the social systems while psychology studies mental systems. The nature of relationship between sociology and psychology still remains controversial and the study of social psychology in relation to both is still unsettled.
There are two extreme views: J.S.Mill believed that a general social science could not be considered firmly established until its inductively established generalizations can be shown to be also logically deductible from laws of mind. Thus he clearly sought to establish primacy of psychology over all other social sciences.Durkheim on the other hand made a radical distinction between the phenomena studied by sociology and psychology respectively. Sociology was to study social facts defined as being external to individual mind and exercising the coercive action upon them, the explanation of social facts could only be in terms of other social facts not in terms of psychological facts. Society is not simply an aggregate of individuals; it is a system formed by their association and represents a specific level of reality possessing its own characteristics. Thus sociology and psychology are totally separate disciplines.
Most sociologists however have adopted various intermediate positions. According to Ginsberg many sociological generalizations can be more firmly established by being related to general psychological laws. Similarly Nadel argued that some problems posed by social enquiry can be illuminated by a move to lower levels of analysis viz psychology and biology. German scholars like Weber came to believe that sociological explanations can be further enriched if an attempt is made to understand social behavior in terms of underlying meanings. Such understanding was conceived in terms of common senses psychology but Weber was not opposed to the development of a scientific psychology in broad sense and Weber was even sympathetic to some of the Freud's ideas. Similarly the interdependence of sociology and psychology for the study of human behavior is given still greater prominence.
The divergence between sociology and psychology can be illustrated from various studies. In the study of conflict and war there have been mutually exclusive sociological and psychological explanations. In the studies of stratification and political behavior the two disciplines have remained divergent. According to Bottomore in almost every field of enquiry it can be shown that psychology and sociology continue for the most part and two separate universes of study. However some attempts have been made to bring them together. One of the most valuable works is of Gerth and Mills. According to them the study of social psychology is an interplay between individual character and social structure and it can be approached either from the side of sociology or from the side of biology. They have even suggested the concept of role to bridge the gap between the two sciences. Social role represents a meeting point of the individual organism and the social structure and it is used as a central concept and social structure in the same terms. Yet in spite of these efforts sociology and psychology continue to offer alternate accounts for behavior and if they are to be brought closer together, it will be necessary to work out more rigorously the conceptual and theoretical links between them.