Permissibility Is the Only Feasible Deontic Primitive

How many concepts do we need in ethics? Take the basic deontic concepts, that is, moral obligation and permissibility. Do we need both of these concepts in our ethical theorizing, or could we make do with just one of them? 1 A standard view is that these concepts are interdefinable —that is, either of them could be defined in terms of the other. On this view, either of obligation and permissibility could serve as a deontic primitive, allowing the other concept to be defined in terms of this primitive. More specifically, obligation and permissibility are usually thought to be interdefinable with the following duality definitions: 2