In this paper, I consider Aquinas’ account of the sin of definite malice, which presupposes that the agent acts in the full knowledge that what he is doing is contrary to the demands of moral reason and divine law (Summa theologiae II-II 156.3). This kind of sin may not stem from a vicious habit, but in many cases, it does. In such a case, the individual’s overall aim in life is constituted by a way of life which he knows to be morally problematic, but which he nonetheless regards as the kind of life he wants to live. Thus, someone who sins from definite malice is not weak or inconsistent, nor is he just mistaken about the real character of his comprehensive good. It is entirely possible for someone to have a correct theoretical understanding of one’s final end, and yet to incline towards a distorted or incomplete version of human perfection as one’s own end (ST I-II 72.5). In such a case, the distorted disposition of the will presupposes some kind of intellectual conception of the good, along the lines that this is the way of life that suits me, or the way of life that I really admire, or that I find rewarding here or now (ST I-II 78.3). The agent lives a life of meaning and purpose, but in such a way as to foster a life of vice, rather than virtue. In this paper, I defend Aquinas’ account of settled malice and vicious disposition theoretically, and considered as a psychological possibility. In order to do so, I draw on an example taken from a mid-century novel by the best author you never heard of, namely, To Bed with Grand Music by Marghanita Laski.