A social constructionist approach is the perspective that many of the characteristics and groups that shape society are inventions of the people living within it in order to create a hierarchy. Race, sexual orientation, class, gender and even mental illness are just a few examples of things that have been postulated to be social constructs and do not exist in reality. In essence, society is a conglomeration of perspectives.
In contrast, the Thomas Theorem, first presented by sociologist W.I. Thomas, says that to a certain extent, what people perceive is real. In other words, if society perceives that someone is of a certain race based on appearance or skin color, then that person is. While the theorem seems to contradict the idea of social constructionism, to a certain extent, it confirms it. It does not put forth the idea that race is not a construct of society. Rather, it acknowledges that if society perceives that the construct has validity, it embraces it. Thomas furthermore asserts that a large part of who or what man is is due to conditioning and circumstance. In its most basic form, social constructionism is a branch of the classic nature versus nurture argument. It is a debate of how much of a person's character is shaped by the innate versus the taught.