This essay explores a remarkable congruence between Macbeth and the teachings of Thomas Aquinas on the nature of virtue, temptation and evil, natural law, and the relationship of the natural to the supernatural. Macbeth's virtue is problematic in that initially he seems courageous when on the attack in battle. But in reality he shows the excessive vice of boldness, and subsequently he fails to manifest courageous endurance and patience in clinging to the good, drifting rather into restlessness and impatience. Aquinas defines evil as a privation of the good. Macbeth persistently chooses apparent good over real good, as he is tempted by the witches and Lady Macbeth. He violates the natural law and suffers extrinsic and intrinsic punishment, a conception linking the play with Aquinas rather than Hooker and Locke. Furthermore, his decline into evil mirrors Aquinas conceptions of the order of punishments following on violation of the natural law, evident in the progressive loss of eternal happiness, virtue, reason and physical and material goods. Finally, the play is not naturalistic but portrays the witches and Macbeth's opponents as instruments of the supernatural.