The problem of the first sin is the problem of how the very first sinful act is even possible, given various Christian axioms about the goodness and creative power of God, and various philosophical assumptions about the nature of freedom and moral responsibility. The problem of the first sin is sometimes treated as a question about the fall of Satan. It turns out to be surprisingly difficult to explain how Satan—by hypothesis, an angel created by God with a rational intellect, an upright will, and wholly good desires and dispositions—could ever make the sinful choice to reject God. Augustine (City of God, Book 12), Anselm (“On the Fall of the Devil” De casu diaboli), and Duns Scotus (Ordinatio 2, dist. 6, q. 2 ) all wrestle with this problem. Contemporary philosophers who try to improve on their efforts include Barnwell (2009, 2017), MacDonald (1999), Rogers (2008), and Timpe (2012). Their responses all seek to explain how Satan’s choice is metaphysically possible, by appealing to their own favored accounts of human freedom and conscious attention. Wood (2016) further distinguishes between the “hard problem” of how Satan’s sinful choice is metaphysically possible, and the “harder problem” of how it can be subjectively rational—rational from the point of view of Satan himself.