 Of course, there is a sense in which human beings do instantiate essences, as Heidegger’s phrase already  admits.[7]  But what matters for existential thought is the manner of such instantiation, the way of existing. What this means can be seen by contrasting human existence with the modes of being Heidegger terms the “available” (or “ready-to-hand,” zuhanden) and the “occurrent” (or “present-at-hand,” vorhanden). Entities of the first sort, exemplified by tools as they present themselves in use, are defined by the social practices in which they are employed, and their properties are established in relation to the norms of those practices. A saw is sharp, for instance, in relation to what counts as successful cutting. Entities of the second sort, exemplified by objects of perceptual contemplation or scientific investigation, are defined by the norms governing perceptual givenness or scientific theory-construction. An available or occurrent entity instantiates some property if that property is truly predicated of it. Human beings can be considered in this way as well. However, in contrast to the previous cases, the fact that natural and social properties can truly be predicated of human beings is not sufficient to determine what it is for me to be a human being. This, the existentialists argue, is because such properties are never merely brute determinations of who I am but are always in question. Who I am depends on what I make of my “properties”; they matter to me in a way that is impossible for merely available and occurrent entities. As Heidegger puts it, existence is “care” (Sorge): to exist is not simply to be, but to be an issue for oneself. In Sartre’s terms, while other entities exist “in themselves” (en soi) and “are what they are,” human reality is also “for itself” (pour soi) and thus is not exhausted by any of its determinations. It is what it is not and is not what it is (Sartre 1943 [1992, 112]). 