“I can be expected to look for truth but not to find it.”

“Staircase wit: the witty riposte one thinks of only after leaving the room.”

Denis Diderot · The source reads: “L'esprit de l'escalier. Staircase wit.” · The witty riposte one thinks of only when one has left the drawing-room and is already on the way downstairs, in 'Paradoxe sur le Comèdien' (written 1773-8, published 1830).