King James claims that witches are driven by greed and envy, sorcerers by curiosity. The witches of Macbeth seem so knowing, so intimate with dark powers, that they have little curiosity; they seem less like crabby old women in Satan's thrall than like avatars of Satan himself. But Macbeth is consumed by curiosity—after the witches provoke curiosity in him, by riddling him with oracles that seem to offer open predicates of identity. (Marjorie Garber has noted, quite correctly, that many of the traditional attributes of witches are “displaced onto the ‘real’ figure of Lady Macbeth”; I think it is also true that some of them are displaced onto her husband.) Shakespeare's play, then, concerns three witches who tease a brave man into becoming a kind of sorcerer.

How can sorcerers know the future? How can Satan himself know the future? James spent a good deal of hard thought in trying to answer those questions:

Satan knows the future only derivatively, either as a good empiricist with a fund of thousands of years of experience to compute the probabilities of events, or as an instrument of God's will in testing the virtue of mankind.