R.K.Merton took the help of biological sciences to define the term 'Function' in sociology. He explained that the function is the contribution of social institutions to society, just like the contribution of organic process inside the human body for the survival of human beings.
Merton says that functions of the social institutions maintain the society and the contributions bring order, unity and cohesiveness in society. Society is constituted by innumerable parts like economy, polity, religion, education, family etc. These parts are not isolated, but are interconnected with each other. Each part has a different function to contribute to society. For example, education has a function, because it prepares the child to adapt to the society. All these functions of social institutions together helps in maintaining the society.
Merton argues that the function of a social institution can be better said by observer than the participant. Because participants may believe that their own subjective motives are the real objective motives of the social institution. For example, children may think that the function of the school is to make friends, whereas the real objective function of the school is to impart knowledge in children for the society's sustenance. Hence, social scientists should look beyond the subjective motives of the participants and need to know the objective consequences of the social forms. To know this, one needs to question self that how really does the institution contributes to the cohesiveness of the society.
Merton criticizes the traditional postulate of universal functionalism that says 'All social or cultural forms have necessarily positive functions. According to Merton, not all social structures have positive functions. Rather, some social forms contribute to society in a negative way. If we observe the caste system of India, it does not contribute anything positive to the society, instead it threatens the democratic values of the society. So, caste system may be classified as dysfunctional. Hence, we can say that some social institutions has dysfunctions too.
Manifest function is something, which can be noticed easily. Latent function is deeper and not all the participants are aware of it. Whereas manifest function is known by all participants of the social institutions. For example, if a criminal is punished, everyone knows that it is the society's way of saying that deviance of behaviour is not permitted in society. This is manifest function. But the latent function of this punishment upholds the society's faith in its collective conscience. Social scientists need to know beyond the common sense perception of the participants and observe the latent consequences of social structures.