The Thomistic Institute The Natural Law Ethics of Killing – Prof. Christopher Tollefsen
Feb 5, 2026
Christopher Tollefsen, Professor of Philosophy and Thomistic natural law scholar, explores whether intending the death of an innocent is ever morally permissible. He contrasts Augustine and Aquinas on lying and killing. He explains the doctrine of double effect, intention versus side-effect, self-defense, public authority to use force, and how human dignity informs an absolute prohibition on intending death.
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Absolute Norm Against Intending Death
- Christopher Tollefsen argues for an absolute norm: it is always wrong to intend the death of an innocent human being.
- He claims this absolute norm should bind both private citizens and public authorities symmetrically.
Double Effect Protects Self-Defense
- Tollefsen explains Aquinas' formulation of double effect: an act's moral species follows the agent's intention, not side effects.
- Thus self-defense can be permissible if death of the aggressor is a foreseen but unintended side effect.
Intent Depends On Action's Means Structure
- Tollefsen distinguishes actions by their nested means: using force to repel an attacker differs structurally from killing as a means to an end.
- He argues that repelling an attack can exclude intending the attacker's death even when lethal force is foreseen.
