A disease-based explanation of substance use disorders is dominant in many Western countries, especially in treatment settings. Acceptance of the disease concept of SUD reduces the shame and guilt of suffering individuals, a definite benefit for treatment of the disorder. Genetic and neurological factors are basic to the disease concept of SUD. However, less severe SUD can result from factors other than a disease process, and is better explained as a behavioral disorder. Even addiction – the most extremely disordered use of drugs – is influenced by developmental, experiential, and societal factors. Basic tenets of disease theory are of limited validity, including that SUD is always a primary disorder (not caused by a psychological disorder), that progression of the disorder is inevitable, and that addictive drug use is uncontrollable. Compulsive behavior and poor impulse control are common in SUD. However, many instances of drug use by addicted individuals require deliberation and apparent full control, especially when the behavior occurs in a non-drugged state. Judgment is often impaired by addiction, but behavior is rarely actually uncontrolled.

Chapter 2 argues that Thomas’s mature view of the formal cause of original justice created an unresolved problem for his doctrine of original sin. Though his early writings sharply distinguished the rectitude of the human will in the state of original justice from supernatural sanctifying grace, by the mid-1260s (e.g., STh I, q. 95, a. 1) he implied that the formal cause of original justice is sanctifying grace. The problem is that Thomas also held (1) that Adam should have been the principal cause of original justice in his posterity and (2) that no creature can be the principal cause of sanctifying grace. Thomas’s mature view implies that the disposition to original justice never could have been sexually transmitted. This implies that his account of original sin as a whole needed to be modified. Adam’s failure to transmit the disposition to original justice rendered the lack of original justice sinful in his posterity: if Adam couldn’t have done this in the first place, how could his descendants have original sin?