David Lewis (1941-2001) was Class of 1943 University Professor of Philosophy at Princeton University. His contributions spanned philosophical logic, philosophy of language, philosophy of mind, philosophy of science, metaphysics, and epistemology. In On the Plurality of Worlds, he defended his challenging metaphysical position, "modal realism." He was also the author of the books Convention, Counterfactuals, Parts of Classes, and several volumes of collected papers.

A defense of material implication as implication.

This paper addresses a problem about epistemic warrant. The problem is posed by philosophical arguments for externalism about the contents of thoughts, and similarly by philosophical arguments for architecturalism about thinking, when these arguments are put together with a thesis of first person authority. In each case, first personal knowledge about our thoughts plus the kind of knowledge that is provided by a philosophical argument seem, together, to open an unacceptably ‘non-empirical’ route to knowledge of empirical facts. Furthermore, this unwelcome (...) prospect of transferring a ‘non-empirical’ warrant from premises about our own mental states and about philosophical theory to a conclusion about external environment or internal architecture seems to depend upon little more than the possibility of knowledge by inference. (The use of the scare-quoted term ‘non-empirical’ is explained a couple of paragraphs further on.). (shrink)

In this paper, I argue that content externalism and privileged access are compatible, but that one can, in a sense, have privileged access to the world. The supposedly absurd conclusion should be embraced.

Written over the last 18 months of his life and inspired by his interest in G. E. Moore's defence of common sense, this much discussed volume collects Wittgenstein's reflections on knowledge and certainty, on what it is to know a proposition for sure.