Satre: Nature vs. Nuture

Satre's philosophy on how man makes the choices in his life and how he is in control of who he is and his nature makes me think about the Nature vs. Nurture argument. It is common for us to blame one of the two for why a person is the way they are, it's either how they were born or it's because of how they were brought up. Can Satre be right in basically saying that it is neither? That is something I still haven't decided. Part of me wants to agree with Satre but then again I feel there has to be a reason for everything.