We are communal beings

The Cartesianism Heidegger targets throughout his treatise [Being and Time] famously revolves around the conception of a self-possessed subject: I am who I am first; I am affected by the world second. But if, as Heidegger contends, this conception is untenable, if, on the contrary, affectedness is ontological or basic then it follows that people are among the things which affect me at my very core. The corollary of the Cartesian affirmation that I am who I am first and affected by the world second is that I am first in isolation and second in community...[But] we are not free-floating subjects who flit in and out of community at will. Rather, in the crowd is where we find ourselves. Accordingly, ‘concern’ for another person, him or her mattering to us, in not an option we select. It is intrinsic to our way of being; it is natural for us.—Ethics at the Beginning of Life, page 101