University of Notre Dame

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Ignorance in Action: A Thomistic Theory of Moral Culpability

posted on 2024-02-09, 13:06 authored by Nicholas Ogle

This dissertation explores a question that lies at the heart of moral theology: when is someone blameworthy for acting in accordance with an erroneous conscience? Drawing upon Thomas Aquinas’s account of human action and moral responsibility, it retrieves and develops a distinctively Thomistic theory of moral culpability that avoids the common pitfall of assuming that sincerity of conscience always excuses wrongdoing, while providing a rational basis for practices of accountability that protect human dignity and promote the common good. Reading Aquinas alongside various modern and contemporary thinkers, the dissertation not only makes an original contribution to research in Thomistic ethics, but also intervenes in contemporary theological and philosophical debates about the nature and scope of moral responsibility.

The argument of the dissertation unfolds in two parts. In Part One, I show how the two dominant theories of culpability in modern moral theology fail to adequately account for our commonsense judgments regarding when someone who makes a moral mistake (i.e., acts in accordance with a sincere, yet erroneous conscience) is deserving of blame. The fundamental problem with these theories, I argue, is their adoption of a “volitional” approach, which assumes that acts of unwitting wrongdoing are culpable only insofar as they are the intentional result or expression of a prior decision. Although such an approach captures an important aspect of our moral experience, insofar as it affirms the possibility of an innocent moral mistake, I conclude that it fails to adequately explain the culpability of sins resulting from grave negligence.

In Part Two, I undertake a systematic analysis of Aquinas’s account of human action and moral responsibility, with the aim of retrieving the theory of moral culpability that informs it. This theory, I argue, rejects the assumption that an agent’s culpability can be determined simply by analyzing the operations of her will, and instead adopts a “normative” approach, which also takes into account our considered judgments regarding what an agent can be reasonably expected to know about her behavior, given the circumstances in which she deliberates and acts. Although this approach leads Aquinas to flatly reject the possibility of a good-faith moral mistake, I argue that when his assumptions about the availability of moral knowledge are suitably revised, his moral theory can provide the basis for a more nuanced position, which does justice to our shared intuitions about when someone who acts in accordance with an erroneous conscience is deserving of blame.


Date Modified


Defense Date


CIP Code

  • 39.0601

Research Director(s)

Jean Porter


  • Doctor of Philosophy

Degree Level

  • Doctoral Dissertation

Alternate Identifier


OCLC Number


Program Name

  • Theology

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