Diagonals: truth-procedures in Derrida and Badiou -- Badiou: truth, ethics, and the formal imperative -- Deconstruction, logic and ordinary language: Derrida on the limits of thought -- Tractatus mathematico-politicus: Badiou's being and event -- Of supplementarity: Derrida on truth, language, and deviant logic -- Summa pro mathematica: further perspectives on being and event