Being and Time raises the problem of "authenticity," that is, the potentiality or otherwise for mortal "Dasein" to exist "fully" enough that it might actually understand being. Heidegger is clear throughout the book that nothing makes certain that "Dasein" is capable of this understanding. Finally, this question of the authenticity of individual "Dasein" cannot be separated from the "historicality" of "Dasein". On the one hand, "Dasein", as mortal, is "stretched along" between birth and death, and thrown into its world, that is, thrown into its "possibilities", possibilities which "Dasein" is charged with the task of assuming. On the other hand, "Dasein's" access to
Being in itself 'Being in itself' to be at the same time the most vague and general concept possible to contemplate, but also the topic of greatest interest to him as a philosopher. In Sartrean existentialism, being-in-itself ("être-en-soi") is also contrasted with the being of persons, which he describes as a combination of, or vacillation or tension between, being-for-itself ("être-pour-soi") and being-for-others ("I'être-pour-autrui"). Being-in-itself refers to objects in the external world — a mode of existence that simply is. It is not conscious so it is neither active nor passive and harbors no potentiality for transcendence. This mode of being is relevant to