 (P1) is a deontic principle of non-contradiction (RW IV, 264 f.); (P2) is the principle that “ought implies permitted” (RW I, 236); (P3) is a kind of combination principle for ought (RW I, 229 f.); (P4) is the “ought implies can” principle (RW I, 230, 257, RW IV, 214, and WL II, 348); and (P5) is a deontic entailment principle (RW I, 229, WL II, 339, 348).