JOHN CORCORAN, Two-method errors.

  Where there are two or more methods for the same thing, sometimes errors occur if two are mixed. Two-method errors, TMEs, occur in technical contexts but they occur more frequently in non-technical writing. Examples of both are cited.

  We can say “Abe knows whether Ben draws” in two other ways: ‘Abe knows whether or not Ben draws’ or ‘Abe knows whether Ben draws or not’. But a TME occurs in ‘Abe knows whether or not Ben draws or not’.

  We can say “Abe knows how Ben looks” using ‘Abe knows what Ben looks like’. But a TME occurs in ‘Abe knows what Ben looks’ and also in ‘Abe knows how Ben looks like’. Again, we can deny that Abe knows Ben by prefixing ‘It isn’t   that’ or by interpolating ‘doesn’t’. But a TME occurs in trying to deny that Abe knows Ben by using ‘It isn’t that Abe doesn’t know Ben’.

  There are two standard ways of defining truth for first-order languages: using finite sequences or infinite sequences. Quine’s discussion in the 1970 first edition of Philosophy of logic [3] and previous lectures was vitiated by mixing the two (see [1]). This error, which had eluded Quine’s colleagues and students, was corrected in the 1978 sixth printing (see [2]). But Quine never explicitly acknowledged, described, or even mentioned the error. Other reviewers did not analyse the nature of Quine’s error.

  This lecture presents and analyses other two-method errors in technical and non-technical contexts.

  [1] JOHN CORCORAN, Review of Quine’s 1970 Philosophy of Logic. In Philosophy of Science, vol. 39 (1972), pp. 97–99.

  [2] JOHN CORCORAN, Review of sixth printing of Quine’s 1970 Philosophy of Logic. In Mathematical Reviews MR0469684 (1979): 57 #9465.

  [3] WILLARD VAN ORMAN QUINE, Philosophy of logic, Harvard, 1970/1986.