By the way, I'm no expert, but I would say that within Sartre's revolutionary ideas, the core is that none of us really exist. By which he meant that there is no "you" -- no essential identity that exists in some pure form separate from context. Instead, there is only the story of what you tell yourself that you are (not how he put it, but this is filtered through my own understanding). The story is really seductive -- so much so that you convince yourself that it has concrete form, that there is a "you", indistinguishable from the story of you. However, if you just decide to be different then you are different. The only true freedom people have is the freedom to choose, but this freedom is absolute.