In this letter to Solomon, Lewis reflects on disagreement in philosophy and ascribing mental states to turkeys.

Disagreement in Logic and Philosophy

Lewis believes that philosophical disagreements often reach a deadlock where neither side will move. Lewis here points to the deadlocked debate over paraconsistency. Such logics allow some contradictions to be true. Lewis remarks that `the mathematical tale is wagging the philosophical dog’, because he does not think that true contradictions are rational and that open-mindedness in logic is reasonable. But he thinks there is a deep methodological disagreement here. So neither side can win over the other.

Lewis and Moore

Lewis also talks about his view that some common-sense positions are reasonable to maintain even in the face of strong philosophical arguments, based on his interpretation of G.E. Moore. Moore thought that philosophy should not lead us to give up common-sense truth. In a recent paper by two project members, we trace Lewis’s Moorean moves to the influence of the Australian philosopher Armstrong (Janssen-Lauret and MacBride 2018). Lewis famously wanted us to give up philosophical theories we could not believe in our most common-sensical moments (1986: 135). But our paper also argues that there might have been further disagreement between Moore and Lewis about methodology.

G.E. Moore and Susan Stebbing against Lewis

Moore thought the truth of common sense judgements was certain. But we cannot infer from that what the correct analysis of such judgements is (1925: 9). Stebbing, the UK’s first female philosophy professor, developed that suggestion further. She wrote, `Nothing but confusion can result if, in one and the same sentence, we mix up language used appropriately for the furniture of the earth and our daily dealings with it with language used for the purpose of philosophical and scientific discussion’ (Stebbing 1937: 42). Stebbing thought common-sense truths and philosophical analysis don’t lie at different ends of a spectrum. Instead, they operate at different levels. So we conclude Moore and Stebbing would oppose Lewis’s ordering ofopinions from the common-sensical to the philosophical. We must keep hold of common sense truth. But that does not imply a deadlock in debate. We can still have legitimate disagreement over its philosophical analysis.

Paper Reference

Frederique Janssen-Lauret and Fraser MacBride (2018) `David Lewis’s Place in the History of Late Analytic Philosophy’, Philosophical Inquiries, 5(1), pp. 1-22.

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Further References

David Lewis (1986) On The Plurality of Worlds, Oxford: Oxford University Press.

G.E. Moore (1925) `Defence of Common Sense’ in J.H. Moorhead (ed.) Contemporary British Philosophy (2nd Series). London: George Allen and Unwin, pp. 193-223.

L. Susan Stebbing (1937) Philosophy and the Physicists, London: Penguin.