This problem (being’s being a problem for itself) concerns above all the split between quiddity and haecceity, the what and the that, as the irresolvable terms through which being both appears and remains inconceivable in itself or as a whole. Heidegger explains:

The distinction does not happen to us arbitrarily or from time to time, but fundamentally and constantly. . . . For precisely in order to experience what and how beings in each case are in themselves as the beings that they are, we must—although not conceptually—already understand something like the what-being [Was-sein] and the that-being [Dass-sein] of beings. . . . We never ever experience anything about being subsequently or after the event from beings; rather beings—wherever and however we approach them—already stand in the light of being. In the metaphysical sense, therefore, the distinction stands at the commencement of Dasein itself. . . . Man, therefore, always has the possibility of asking: What is that? and: Is it at all or is it not?(FC, 357)

Sorrow and definition trace contrary movements across this fundamental distinction. They toss, with symmetrical trajectories, the same coin of this always possible double-sided question. Where definition gives the what of a that (the bird is a robin), sorrow experiences the that of a what (the robin is dead). Accordingly, definition entails a kind of sorrow, elicits a refusal of something that happens against our will, namely, of the substance of the definition that, however proper, we disagree with as not providing the thing defined.

¶ 1:58 AM