Its descriptive method moves from the most abstract to the highly concrete. It begins by analyzing two distinct and irreducible categories or kinds of being: the in-itself (en-soi) and the for-itself (pour-soi), roughly the nonconscious and consciousness respectively, adding a third, the for-others (pour-autrui), later in the book. He concludes with a sketch of the practice of “existential psychoanalysis” that interprets our actions to uncover the fundamental project that unifies our lives.
Being-in-itself and being-for-itself have mutually exclusive characteristics and yet we (human reality) are entities that combine both, which is the ontological root of our ambiguity. The in-itself is solid, self-identical, passive and inert. It simply “is.” The for-itself is fluid, nonself-identical, and dynamic. It is the internal negation or “nihilation” of the in-itself, on which it depends. Viewed more concretely, this duality is cast as “facticity” and “transcendence.” The “givens” of our situation such as our language, our environment, our previous choices and our very selves in their function as in-itself constitute our facticity. As conscious individuals, we transcend (surpass) this facticity in what constitutes our “situation.” In other words, we are always beings “in situation,” but the precise mixture of transcendence and facticity that forms any situation remains indeterminable, at least while we are engaged in it. Hence Sartre concludes that we are always “more” than our situation and that this is the ontological foundation of our freedom. We are “condemned” to be free, in his hyperbolic phrase.
We can look at the in-itself and the for-itself in terms of self-reference. Any autopoietic system possesses self-referentiality; it has a sense of self as a being different from everything else in its world. Thus it has self-reference and other-reference. The sense of self (the for-itself) can never be identical to the in-itself. The in-itself has no sense of doubleness, self and not-self.
Being “always ‘more’ than our situation” is about structural determination. I might be locked in a prison cell (this would be my given situation), but my response to this situation is self-determined (or structurally determined). The structures are my expectations; so if I always expected to be in prison (and it feels normal), then I shouldn’t be bothered by the fact that I’m in prison. So we have a given situation and a horizon of possibilities for what might follow.