Heidegger redefined Being as mere not-ness because nominalism blocked its traditional meaning.

Evidence

Karl Heinz Haag, a student of his who was now his research assistant, had trenchantly demonstrated in his work the way in which Heidegger made a virtue of necessity: since he was unable to conceive of Being in its traditional meaning, as a result of nominalist criticism, he defined it as the not-ness' of entitiesas that which was pure mediation, transitive being, unique in its sudden change into the entity of existing’ Being. — Rolf Wiggershaus, The Frankfurt School, 627

Categorization

• DEFINE: Names Karl Heinz Haag as Adorno’s research assistant and the precise construction of Heidegger’s Being as ‘not-ness’ following nominalist critique — a specific, datable intellectual-historical claim.
• XREF: connects to: Heidegger’s nothingness nihilates itself rather than being a Being; Heidegger’s pure Being is actually hyper-mediated, not immediate — Rolf Wiggershaus, The Frankfurt School: Its History,…, 2509; Heidegger framed being as a question meant to astonish rather than to be answered — Sarah Bakewell, At the Existentialist Café: Freedom,…, 173
• yield-rescued: below the book’s yield-target cutoff, included anyway for connecting to: Heidegger’s nothingness nihilates itself rather than being a Being; Heidegger’s pure Being is actually hyper-mediated, not immediate — Rolf Wiggershaus, The Frankfurt School: Its History,…, 2509; Heidegger framed being as a question meant to astonish rather than to be answered — Sarah Bakewell, At the Existentialist Café: Freedom,…, 173

Broader Connections

• Heidegger’s pure Being is actually hyper-mediated, not immediate #complicates (0.73) — Rolf Wiggershaus, The Frankfurt School, 2509