Karl Marx.

I believe that acting a certain way has noticeable effects on the way you think and your thought process. Marx ten theses (historical materialist determinism, organicism, class struggle, the pivotal role of capitalism, value theory, alienation, oppression, revolution, dictatorship, and communism) are very important to his statement, "It is not the consciousness of men that determines their being, but on the contrary, their social being that determines their consciousness." 

The way that a person thinks about themselves, their social standing, and how other people perceive them is more important than anyone thinks.