Negligent omissions, cases in which an agent unintentionally forgets to fulfill an obligation, are philosophically problematic. They are problematic because they are considered blameworthy despite the fact that the conditions for voluntariness often appear unfulfilled. In an attempt to explain how they may be voluntary, this book delves into the action theories of Aristotle, Anselm, Aquinas, Scotus, and Suárez. In doing so, not only is the philosophical (and theological) importance of negligent omissions demonstrated via new and insightful interpretations, but a complex model for explaining the voluntariness of negligent omissions is constructed. The result is an original solution to the problem of negligent omissions that demonstrates the utility of appealing to historical approaches to solve contemporary philosophical and theological problems.