There is a very close relationship between these two. But, that does not mean that ethics is a branch of sociology.
According to the evolutionist, the present ethical behaviour of man is only a development from his prehistoric animal behaviour. But this idea is fallacious even though from the historical point of view, ethics and sociology spring from the same source, there is a fundamental difference between the two, a fact forgotten by people who hold this opinion.
The difference between ethics and sociology are the following:
1. Sociology is a positive science, ethics is normative one:
Normative sciences study ideals and positive sciences study facts. Sociology gives factual knowledge of social relations while ethics evaluates them upon the criterion of ethical ideals. It decides the good and evil in social conventions, habits, relations, traditions etc. In this way, sociology and ethics are related to each other but their scope does not coincide.
2. Ethics is more comprehensive than sociology:
Sociology is a comparatively theoretical study while ethics very much affects our practical life. It tries to seek the, ultimate good and in its light makes judgement concerning virtues, duties of the individual and state, good and bad of social institutions conventions, authority and economic and political laws etc. In the form of science of ethical ideals it is also related to philosophy.
3. View points of sociology and ethics are different:
Sociology studies man as a member of society. Ethics studies man as a responsible individual having freedom of will.
4. Scope of Sociology and ethics are different:
Sociology is an objective science where as ethics is a subjective science. Social science studies objective mental process and conventions, laws organisation etc. The subject of ethics is internal motives, desires, volitions and man's independently willed behaviour in the context of intentions.
5. The methods of sociology and ethics differ:
The method of sociology is historical, scientific and empirical. The method of ethics is teleological, scientific as well as philosophical, empirical as well as transcendental. It is descriptive and critical.
Sociology, like other positive sciences, looks into a cause effects relation is the facts. Ethics gives them their place in the World and comparing them to the ultimate good, describes ethical facts. Sociology shows the evolution of human behaviour and ethics evaluates it in the light of the ultimate good.
Sociology studies the external behaviour of man, while ethics emphasises the internal aspects. Thus ethics cannot be said to be a branch of sociology.