Heidegger, in his main work "Being and Time", in his quest to re-pose the original pre-Socratic question of Being, wondered at how to meaningfully ask the question of the meaning of being, since it is both the greatest, as it includes everything that is, and the least, since no particular thing can be said of it. He distinguishes between different modes of beings: a privative mode is present-at-hand, whereas beings in a fuller sense are described as ready-to-hand. The one who asks the question of Being is described as "Dasein" ("there/here-being") or being-in-the-world. In his later thought, he criticizes the distinction between Being and beings, uniting them in the quasi-pre-ontological notion of Beyng. Beyng is disclosed in the Event (Ereignis) of. Appropriation, as the original occurrence of Being. Sartre, popularly understood as misreading early Heidegger (an understanding supported by Heidegger's essay "Letter on Humanism", which responds to Sartre's famous address, "Existentialism is a Humanism"), employs modes of being in an attempt to ground his concept of freedom ontologically by distinguishing between "being-in-itself" (things), and "being-for-itself" (man).