Borys Jastrzębski

Frege’s Commitment Puzzle concerns inferences from sentences such as “Jupiter has four moons” to sentences such as “The number of moons of Jupiter is four”. Although seemingly about completely different things, such pairs of sentences appear to be truth-conditionally equivalent. In this paper, I make a case against versions of the Puzzle that appeal to properties and propositions. First, I argue that propositions in Frege’s biconditionals serve a specific, non-referring conversational role. Second, I claim that the existence of properties derived from Frege’s equivalences relies on a controversial philosophical premise. Third, I contend that it takes more than conversational interchangeability for two sentences to be equivalent and that genuine equivalence has not been established for non-numerical versions of Frege’s biconditionals. I conclude by suggesting that, being restricted to numbers, the Commitment Puzzle may be classified as a local oddity.

Comprehensive Linguistic Approach to Frege's Commitment Puzzle There is a puzzle, noticed by Frege, about inferences from sentences like (F1) "Jupiter has four moons" to sentences like (F2) "The number of moons of Jupiter is four". They seem to be truth-conditionally equivalent but, apparently, they say something about completely different things. (F1) seems to be about moons, while (F2) about numbers. This phenomenon raises several puzzles about semantics, syntax, and is one of main tools of easy ontology. Recently, new linguistic and pragmatic solutions were proposed. Linguistic solutions of Thomas Hofweber and Katharina Felka are refreshed versions of the traditional paraphrastic approach that involve consideration of conversational contexts as well as syntactical structure of copular sentences. The pragmatic solution resorts to bracketing or indifference to certain possible alternatives and contexts of a sentence. I discuss their strong and weak points and propose to include in further research John Biro's account of the expression "the number of planets", which solves the problems of the new linguistic approaches.