D. In doing x an agent acts incontinently if and only if: 1) the agent does x intentionally; 2) the agent believes there is an alternative action y open to him; and 3) the agent judges that, all things considered, it would be better to do y than to do x.

Some philosophers, for example Quine, doubt the possibility of jointly using modalities and quantification. Simple model-theoretic considerations, however, lead to a reconciliation of quantifiers with such modal concepts as logical, physical, and ethical necessity, and suggest a general class of modalities of which these are instances. A simple axiom system, analogous to the Lewis systems S1 —S5, is considered in connection with this class of modalities. The system proves to be complete, and its class of theorems decidable.