In telling a story one of the most successful devices for easily creating uncanny effects is to leave the reader in uncertainty whether a particular figure in the story is a human being or an automaton and to do it in such a way that his attention is not focused directly upon his uncertainty, so that he may not be led to go into the matter and clear it up immediately.
Ernst Jentsch, Zur Psychologie des Unheimlichen
automaton, device, effect, literary, mystery, reader, reality, secret, uncanny, uncertainty, unheimlich