‘Nothing is but what is not’. These words uttered by Macbeth after his bizarre first encounter with the three weird sisters could serve as a motto for the whole of Shakespeare's tragedy; for ‘the Scottish play’, as the superstitious have called it for centuries, is ruled by uncertainty, the questionable, the netherworld, where the only thing that is absolute is evil. It is about ambiguous forces that violate ife's natural order – witches, ghosts, a moving forest, an invisible dagger – what we call the macabre, what Freud called the uncanny, and what Verdi called ‘un genere fantastico’. Shakespeare constructs a world of binary opposites where boundaries, as Marjorie Garber has observed, are ‘continually transgressed, and marked by a series of taboo border crossings’.