Relating gesture to speech: reflections on the role of conditional presuppositions

In his paper Gesture Projection and Cosuppositions,' Philippe Schlenker argues that co-verbal gestures convey not at-issue content by default and in particular, that they trigger conditional presuppositions. In this commentary, I take issue with both of these claims. Conditional presuppositions do not supply a systematic means for capturing the semantic contribution of a co-verbal gesture. Some gestures appear to contribute content inside of a negation when their associated speech content is likewise embedded; in other cases, co-verbal gestures arguably contribute unconditional content to the global level. When this happens, we can infer what might look like a conditional presupposition, but this inference follows naturally from general principles already at work in purely verbal discourse and does not justify the claim that gesture content is contributed to a conditional presupposition. Problems exposed in the discussion of conditional presuppositions show that we are not yet in a position to make a general claim about the at-issue status of co-verbal gestures.