You are talking to a wall. This also is found in the Greek collections, and also in the form 'to talk through the wall.' It used to be said about anyone who did something particularly absurd. Perhaps it came from lovers, who sometimes talk to the doors and windows, or even the walls of their sweethearts, as if there were understanding in them. Pautus in the Truculentus adopts it in the sense of speaking to one who will keep quiet: 'I will be a wall; you go ahead and talk.'