[Curry examines the Weird Sisters and the precise nature of the evil they embody in Macbeth. The critic argues that Shakespeare's witches are consistent with how Elizabethans envisioned demonic spirits, not as mere hallucinations, but as representatives of an actual evil. Curry also explores the nature of the witches' prophecies in Macbeth, asserting that while their predictions are inherently sinister, only Macbeth can introduce evil into the world by yielding to the temptation of their assertions. The Weird Sisters, the critic continues, represent only on element of the demonic forces which pervade Macbeth; the natural disturbances, Macbeth's visionary dagger, Banquo's ghost, and Lady Macbeth's "demoniacal somnambulism, "or sleepwalking episode, are also manifestations of these evil powers. Taken together, Curry declares, these supernatural phenomena in Macbeth represent the Christian perspective of a world full of objective evil.] That the Weird Sisters possess. . . perennial and astounding vitality is attested...