There’s a famous anecdote about Wittgenstein and his friend Piero Sraffa by Norman Malcolm (Ludwig Wittgenstein: A Memoir): Wittgenstein was insisting that a proposition and that which it describes must have the same ‘logical form’, the same ‘logical multiplicity’, Sraffa made a gesture, familiar to Neapolitans as meaning something like disgust or contempt, of brushing…