Their relationship
The relation of Political Science to Sociology is like the relation of a part to the whole, of a branch to the trunk. As a social being, man performs many social activities which may be studied as a whole or separately. Sociology studies them as a whole; it is the general science of society. It studies the nature, origin and development of society in all its aspects. It studies the individual and the social groups, whether organised or unorganised, conscious or unconscious, economic, religious, political, or intellectual. Political Science also studies society but only politically organised society, called the State.
It studies social acts and ideas but only of political nature. Hence, it is a specialised social science, a part of the general science of Sociology. It deals with the political life of man which is a part of his total social life. Political Science is a ‘differentiation’, i.e., a branch of Sociology. Sociology deals with man as a socius; politics deals with him as a citizen or subject of the State. Sociology deals with all kinds of associations and politics with only one kind of association, viz., the political system or the State. What is political is also social, though what is social is not necessarily political.
For instance, when people assemble at a political party meeting, they are doing something which is both political and social, but when they meet to gossip as friends, they do something which is social, but not political. This is also the reason why we need the science of Politics. The field of Sociology is so vast and comprehensive that it needs a specialist who will devote himself to the study of its political aspect, which becomes Political Science. Both sciences are mutually contributory. Political Science gives to Sociology facts about the organisation and functions of the State, and obtains from it knowledge of the social basis of the State, law and political authority.
So close is this relationship between them that, as Giddings says, a student of Political Science must begin his subject with a study of Sociology, because “to teach the theory of the State to men who have not learned the first principles of Sociology is like teaching astronomy or thermodynamics to men who have not learned the Newtonian laws of motion”. A political scientist must, therefore, be also a sociologist and vice versa. Politics deals with group life, the study of which is the province of Sociology. In short, it is the relation of the part and the whole.
Their differences
Although exact line of demarcation between the two sciences is difficult to draw, yet they are different in some respects: (i) The scope of Political Science is narrower than that of Sociology. Sociology is the science of human beings in their associative processes, while Political Science is the science of politically organised community which has been consciously set up by man. (ii) Sociology is prior to Political Science, because society was prior to the State.
Man was first a social animal and later on a political being, (iii) Political Science assumes that man is a political animal, but Sociology explains how and why he became so and how his political life is affected by his membership in other forms of associations, (iv) Finally, Socidlogy, like history, studies actual social organisations and associations, but political Science aims at a study of the past, present, and future of the political institutions and States. Nevertheless, many of the changes in political thought are due to the influence of sociological studies in recent times, especially in the behavioural theory of power.