Modal Epistemology.

This article discusses modal epistemology. Philosophy abounds in modal arguments. A surprisingly high proportion of these arguments have the following features as they are formally valid; one of their premises is far more controversial than any of the others; it is a model premise. It is not always possible to invert a possibility argument. But it is always possible to replace the crucial modal premise of a possibility argument with the denial of its conclusion and to replace its conclusion with the denial of its crucial modal premise.