 One quick argument is that PAP is self-evident; alternatively, it is immediately known a priori, intuitively obvious, or analytic. Those who deny it are thereby convicted of confusion about moral responsibility, the ability to do otherwise, or both. If PAP does enjoy such a high epistemic status, this explains its wide acceptance in the major historical periods of philosophy, a discipline not usually known for producing even approximate consensus. But in spite of this agreement, the principle has turned out not to be so obvious, and in fact appears to make a substantive, controversial claim about responsibility. Witness some notable dissenters, including the Stoics, Augustine, Aquinas, and Hobbes (see, respectively,  §3.2;  Hunt 1999; Stump 1997; Martinich 2005). Moreover, PAP has come under sustained attack in recent decades due in large part to the early efforts of Frankfurt (1969), Fischer (1982), and Dennett (1984a,b). This is enough to show that, however plausible PAP might first appear, it requires more than this quick defense.