Should I say that? An experimental investigation into the norm of assertion

There is a lively philosophical debate concerning which epistemic norm regulates assertion. Some scholars claim that such norm is factive (and only true propositions are assertable), while others deny this thesis (they contend that assertability does not entail truth). There is widespread agreement in the literature that these two opposite hypotheses are empirically testable, and John Turri (2013a, 2013b, 2016a, 2016b) has collected compelling evidence in favour of a factive norm of assertion.This paper makes a negative and positive claim. The negative claim concerns previous evidence found in support of factive norms. We argue that the empirical data collected by Turri does not support his conclusions. Turri drew conclusions about assertability from judgments about whether a given agent 'should' assert something. We argue that there are two possible interpretation of ‘should’, a teleological and a normative one, and that only a normative interpretation of the ‘should’-judgments would support Turri’s conclusion. In experiment 1, we show that the majority of participants in a follow-up study reported that they interpret ‘should’ in a teleological, non-normative way, showing that Turri’s results do not seem to support his conclusions.The positive claim of the paper is that assertion is not regulated by a factive norm. We conducted three test to support this claim. In experiment 2, we modified the temporal structure of Turri’s original vignettes so as to avoid a teleological interpretation of the ‘should’ question. In experiment 3, we introduced three alternative probes, and asked participants whether the speaker ‘ought’ to assert p, and whether it was ‘permissible’ or ‘appropriate’ to do it. The result of both experiments strongly support the non-factive hypothesis against the factive one. However, we also identified some reasons to suspect that our alternative vignettes could also have been interpreted in a way that does not track judgments of assertability. To collect judgments that are unmistakably about assertability, in experiment 4 we explicitly instructed participants that the study was about an epistemic norm regulating assertion, and asked them to judge whether given assertions violated the norm. Consistently with the previous experiments, the results show that participants do not take assertability to require truth.