Trusting others in the sciences: a priori or empirical warrant?

Abstract Testimony is indispensable in the sciences. To deny the propriety of relying on it engenders an untenable scepticism. But this leaves open the issue of what exactly confers a scientist’s epistemic right to rely upon the word of her colleagues. Some authors have suggested a recipient of testimony enjoys an epistemic entitlement to trust the word of another as such, not requiring evidence of her trustworthiness, so long as there is not evidence of her untrustworthiness. I argue that, whether or not such an on-no-evidence entitlement to believe what one is told exists, it shrinks to irrelevance in the explanation of the basis on which scientists take each other’s word in the scientific community. This is so, since a normally knowledgeable adult hearer is typically awash with relevant evidence, direct and circumstantial, for and against, concerning a teller’s trustworthiness, and this swamps any alleged entitlement to believe in the absence of such evidence. There need not be personal knowledge of the teller, since social role and topic provide evidence regarding trustworthiness. I also discuss the individuation of ‘testimony’ as an epistemic kind. I suggest that we should not attempt to define a category with sharp boundaries, but instead characterise a paradigm case—one person telling another something in face-to-face personal communication—and then notice other cases which both resemble and diverge from this in epistemically relevant features—lectures, media broadcasts, personal letters, personal diaries, etc.