This chapter argues the case for a partial overlap between Diderot and Charles Maturin who are conventionally labelled Enlightenment and Gothic. In Diderot's novel, the notion of the automaton is linked to the system of an anti-society of isolated Cartesian cells. And it becomes associated with horror and superstition, a phalanstery of mastery and slavery which anticipates the automatism of the Marquis de Sade. Diderot himself had been imprisoned in Vincennes and unnerved by the experience to the point of apparent capitulation to the authorities, so he had studied at first hand the condition he writes about. Automatism is indeed part of the theatre of terror and the relation between hypocrisy, acting and ritualized behaviour is part of Maturin's meditation. Maturin and Diderot independently share a self-conscious fictional heritage whose master trope is the theatre; this shapes the different questions they ask of the novel genre in a common manner.