• The title of the first of these (pp. 500-505) is a good indication of the content. The error Putnam sees in verificationism lies in his comparison of language with microscopes, and the possibility of stating unrestricted generalizations. (Note that we cannot verify “There are no intelligent extraterrestrials” because it claims there are none anywhere and we can never be sure that we have looked everywhere.) The insight of verificationism is tied to Putnam’s criticism of the idea of truth as a substantive property, amounting to assertibility, that is uniform for all content (see the middle of p. 501).

• The second section (pp. 505-510) is centered on the interpretation of Wittgenstein’s views on mathematics. Wittgenstein notoriously, or famously, appeared to say that proofs could change the subject in mathematics—e.g., that the (far from obvious) construction of a pentagon with straight-edge and compass introduced a new concept “constructible pentagon” rather than uncovering an unrecognized aspect of the pre-existing concept (of a “measurable pentagon” as a figure with five equal sides). Putnam notes that this undermines the ability to distinguish change in meaning from change in belief (p. 507) and points to a discussion of the issue by Cora Diamond as a way out. (Here notice the connection between the idea of “seeing the face” of an activity and the title of this lecture.)

Let me add two comments here. First, Quine’s views about the incoherence of the analytic/synthetic distinction and associated conceptions of meaning have not appeared often in our discussions of truth, but one consequence of his views is the incoherence of the distinction between change of belief and change of meaning, which Putnam seems to take as unquestionable. Second, Cora Diamond later* discussed Putnam’s characterization of Wittgenstein’s views, saying that he didn’t recognize Wittgenstein’s very real sympathy for verificationism.