How do we explain the presence and activity of evil in the world? There are a number of possible answers to this question in early modern England. In Othello (c.1604), I argue that Shakespeare engages with competing contemporary accounts of what evil is, where it comes from, how it works, and why it is permitted in the first place. Reconsidering the play’s theological grammar of evil, and building on recent criticism, I show that Iago’s evil is neither Manichean nor an expression of non-being. To reduce his evil to non-being is to only partially understand the plenum between being and non-being that Iago traverses in the play. Iago needs the good; he feeds off it, is reliant upon it, grammatically and causally. His devilishness is “demi” because he still retains within him that “spark” of divinity that in early modern theology connects the summum bonum to all his works, good and evil alike. In this way, Shakespeare offers a subtle critique of a theodicy that, directly or indirectly, makes God responsible for evil.