Abstract

I develop a predicate logic for formalizing moral arguments. The system makes formal deontic reasoning accessible to non-logicians. Standard deontic logic is rejected as susceptible to deontic "paradoxes," ethical presuppositions , and not modeling contrary-to-duty or "second choice" obligations. I defend the use of predicate logic in place of modal-type deontic operators on two grounds: although operators attach to sentences, which represent states of affairs, our normal talk of duty concerns obligatory actions, which are represented by names properly attached to predicates, and predicate logic is more familiar to every philosopher/ethicist than is modal logic. The form of obligation predicate used is intended to reflect natural-language discussions of duty. For this reason, one of the names to which the predicate attaches is an action name. The agent must also be given a prominent place in any formalization of moral reasoning. I characterize predicates of obligation, performance, prohibition, two types of permission , satisfaction and violation. Doing so, I consider several possibilities for negating actions. Each is deficient. The failure to perform an action is not itself an action. As an adequate action-negating function is necessary to define prohibition in terms of obligation, I conclude that prohibition should be primitive and not defined in terms of obligation. An obligation to act is essentially different from an obligation not to act, and should be represented by a different predicate. In representing obligations in a system more faithful to our ordinary conceptions, I am led to consider issues and distinctions neglected in the literature. For example, some obligations are discharged upon their satisfaction, others require recurrent or continuous satisfaction, and still others elapse. This complexity is reflected in my formal language