Charles Morgan has argued that nonmonotonic logic is ``impossible''. We show here that those arguments are mistaken, and that Morgan's preferred alternative, the representation of nonmonotonic reasoning by ``presuppositions'' fails to provide a framework in which nonmonotonic reasoning can be constructively criticised. We argue that an inductive logic, based on probabilistic acceptance, offers more than Morgan's approach through presuppositions.

This paper has two objectives, neither previously attempted in the published literature—first, to outline J. M. Keynes's theory of knowledge in some detail, and, secondly, to justify the contention that his epistemology is a variety of rationalism, and not, as many have asserted, a form of empiricism. Keynes's attitude to empirical data is also analysed as well as his views on prediction and theory choice. 1This paper is partly based on ideas initially advanced in O'Donnell [1982], a revised and expanded (...) version of which is to be published as O'Donnell [1989]. I should like to thank an anonymous referee for helpful comment, and King's College, Cambridge for permission to quote from the Keynes Papers. (shrink)

This paper tries to extend Hintikka's inductive logic so that we can confirm a causally necessary statement. For this purpose, a joint system of inductive logic and logic of causal modalities is constructed. This system can offer a plausible explication of the distinction between nomic and accidental universality, as well as a good formulation of a causal law. And the transition from actuality to causal necessity is construed, in this system, as essentially probabilistic; i.e. no statements about actuality can entail (...) a necessary statement, but certain statements about actuality can single out a most probable causal law. (shrink)