Omissions and their causes


  • Steven Jensen University of St. Thomas, Houston TX


Aquinas, Ethics, Medieval philosophy, Theory of action, Theology


Several aspects of Aquinas’s teaching on omissions found in the De malo are problematic and conflict with the parallel treatment in the Summa, written at almost the same time. First, Aquinas claims that an omission consists essentially in no action at all. In the Summa, he notes that some omissions consist in no action at all, while other omissions consist in an interior act of will together with the absence of an exterior action. Second, in the De malo Aquinas claims that we cannot directly will an omission. In the Summa, he maintains the more intuitive position that sometimes we can choose simply not to do something. Finally, in the De malo Aquinas claims that the cause of an omission can itself be a morally good action. In the Summa he neither affirms nor denies this claim, but he provides certain clarifications that would qualify any sense in which a good action could cause an omission. This paper examines all three of these claims, as they are treated both in the De malo and in the Summa. The third claim, which concerns a good action causing an omission, occupies the most space. The entire analysis has implications concerning Aquinas’s teaching on the first moral action of an unbaptized child. The treatment of omissions in the De malo cannot account for this first act, at least when it is a sin. The treatment in the Summa, however, provides the tools to account for this first sin.




How to Cite

Jensen, Steven. “Omissions and Their Causes”. Acta Philosophica 22, no. 1 (March 1, 2013): 117–134. Accessed December 6, 2023.