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Aquinas on Conscience

3. Synderesis and Prudence

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In this module we look at two features of practical reason: synderesis and prudence, and examine their significance to Aquinas’ doctrine of conscience. In particular we (i) compare and contrast Aquinas’ respective accounts of synderesis, prudence and conscience (ii) examine how prudence perfects practical reason, by considering the powers of reason and the will in human action (iii) outline the stages of human action (iv) examine the virtues connected to prudence, and (v) review the functions of the three features of practical reason: synderesis, prudence and conscience.


In this course Dr Daniel De Haan (University of Oxford) explores St. Thomas Aquinas’ doctrine of conscience. In the first module we introduce Aquinas’ account of practical reason, and its relevance to the doctrine of conscience. After that, we explore Aquinas’ views on the judgment of conscience in the Summa Theologica. In the third module, we look at two further features of practical reason: synderesis and prudence, before moving on to Aquinas’ take on moral responsibility. Finally, in the fifth module, we look at the demands of conscience in everyday life, and Aquinas’ challenge to ‘moral dilemmas’.


Dr Daniel De Haan is a Senior Research Fellow & Lecturer in Philosophy and Theology in the Catholic Tradition at the University of Oxford. His research interests are in philosophical theology, Christian and religious ethics, and science and religion. His most recent publications include Aquinas on Perceiving, Thinking, Understanding, and Cognizing Individuals (2019), and Approaching Other Animals with Caution: Exploring Insights from Aquinas's Psychology (2019)

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APA style

De Haan, D. (2022, February 23). Aquinas on Conscience - Synderesis and Prudence [Video]. MASSOLIT.

MLA style

De Haan, D. "Aquinas on Conscience – Synderesis and Prudence." MASSOLIT, uploaded by MASSOLIT, 23 Feb 2022,

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