Conscience as an Act of Practical Reason in Aquinas

Abstract

Depending on the type of morality adopted, the role of conscience differs. In the case of virtue ethics, conscience plays a more of a personal role, while in the case of deontology, conscience functions as the seat of moral law and norms. St. Thomas, however, shows the role of conscience in a way that seems to connect these perspectives. The aim of this article is to retrieve the role of conscience in Aquinas against the broad background of Aristotle’s distinction between potency, habitus and act. The structure of the Summa Theologiae follows this distinction. Aquinas begins with human powers, then considers habitus, and finally human acts: cognitive and affective.

This allows us to understand and explain the reasoning of Aquinas contained in I, q. 79, a. 12 “Whether synderesis is a power of the intellectual part?” and a. 13 “Whether conscience be a power?” Aquinas explains synderesis as an innate human habitus, subject to the practical intellect and fulfilling a role analogous to the habitus of the first principles (intellectus principiorum).

Aquinas understands conscience on the level of an act of practical reason. In this way, conscience in the strict sense consists in the act of knowing oneself in terms of good and bad. It is closely related to the act of prudence, which in its action combines general principles, i.e. knowledge of virtues and vices and moral law, with a specific action here and now. Aquinas’ concept allows us to see the possibility of integrating virtue-based morality with deontology in a different way than we are used to.