In The Tempest, magic is a dazzling art form that infuses the play with a sense of wonder and a whole lot of spectacle. (Think "The Sorcerer's Apprentice" in Disney's Fantasia, but better.) This lends itself to a concept developed throughout The Tempest – magic is a craft not unlike that of the playwright. Although Prospero uses magic to control the natural and the supernatural worlds, the play also suggests his art is distinct from the kind of black magic practiced by the witch Sycorax.
Although Prospero uses magic to regain his place in Italy, magic is also the thing that got him into trouble in the first place – if Prospero hadn't isolated himself with his books, he never would have lost his dukedom.
Although the play goes out of its way to differentiate Prospero's studied art from Sycorax's black magic, at times, the play makes us wonder if Prospero and Sycorax don't share more in common.