Abstract

This chapter examines the philosophical trajectory of Ramsey sentences from Frank Ramsey’s original discussion in “Theories” to their later deployment by Rudolf Carnap, David Lewis, and contemporary structural realists. It argues that Ramsey sentences have frequently been appropriated in support of broadly antirealist approaches in the philosophy of science—approaches that either deny or paraphrase theoretical commitments to unobservable entities—even though they cannot ultimately sustain such interpretations. We reconstruct Ramsey’s introduction of his existentialized account of theories against the background of the positivist project of eliminating theoretical terms and emphasize the pragmatist motivations underlying his rejection of explicit definitions. We then examine Carnap’s re-invention of Ramsey sentences as part of his attempt to secure a compatibilist position between realism and instrumentalism and argue that Carnap’ strategy ultimately fails. Finally, we discuss later Ramseyan approaches, focusing on structural realism and Lewis’s “Ramseyan Humility,” and contend that they face serious difficulties, at least when intended as moderate realist positions.