 Let us suppose that we shall never have the Final Theory of Everything before us—at least in our lifetime—and that we also remain unclear (on physical/experimental grounds) as to whether that Final Theory will be of a type that can or cannot be deterministic. Is there nothing left that could sway our belief toward or against determinism? There is, of course: metaphysical argument. Metaphysical arguments on this issue are not currently very popular. But philosophical fashions change at least twice a century, and grand systemic metaphysics of the Leibnizian sort might one day come back into favor. Conversely, the anti-systemic, anti-fundamentalist metaphysics propounded by Cartwright (1999) might also come to predominate. As likely as not, for the foreseeable future metaphysical argument may be just as good a basis on which to discuss determinism’s prospects as any arguments from mathematics or physics.