Abstract
This paper seeks to counter the argument that since Aquinas’s natural law obligations necessarily presuppose the ability of practical reason to prescribe and proscribe for the sake of eudaimonia, it is irrational in cases of inescapable suffering to characterize any natural law obligation as indefeasible. Four possible rebuttals of this argument from suffering are examined; but only three are judged successful. Their key premises are that, as Aristotle and Aquinas pointed out, this life’s eudaimonia is defined in terms of human nature and not in terms of individual psychological conditions, e.g., suffering; that suffering does not negate the rationality of hoping for attaining eudaimonia in the future; and that suffering necessarily precludes neither the virtuous acts that per se constitute this life’s eudaimonia nor the love that enables one to experience eudaimonic joy.