Existence presents itself chiefly as a task – each individual human being tasked with its own project – namely, becoming a self. Insofar as each individual is concerned, his particular project is both determined and un-determined for him. It is determined insofar as the individual always finds itself situated in the world; and thus its project is a thrown project. It is at the same time un-determined insofar as the existing individual self is responsible for his choosing among the existent possibilities. But which meaningful possibilities present themselves to the individual self as real possibilities, is in large part determined by the vast network of meaning-given structures by which the individual understands itself, and its possibilities in the world, at all.
Thus, while I am free to choose for myself whether I take up my understanding of my being-in-the-world as a student, a doctor, a lawyer, a husband, or philosopher; I am not free to choose from among those possibilities for which, on account of my thrownness, do not present themselves to me as meaningful possibilities.
Thus, Sartre is wrong when he concludes that human being’s freedom (of action) is absolute. This presumes that one can get fully behind, or separate from, one’s facticity; but this only evidences Sartre’s latent Cartesianism – and indeed, contributing to his general misreading of Heidegger. In other words, Sartre is unable to move beyond his presupposition of a subject removed, or detached from his situated-ness in the world.
It still suffices to say that human being is doomed to his freedom. Even if our freedom isn’t the absolute freedom that Sartre believes it to be, we are still all alone, abandoned to ourselves, and faced with the same abysmal groundlessness of existence – with only the slight qualification as regards the otherwise tenuous security offered by our facticity.