Testimony: A Philosophical Study

This book is about a topic in epistemology that had been much neglected until its publication, but has subsequently become much more discussed. That topic is testimony, or, less technically, the conveying of information by telling. Coady argues that reliance upon the word of others plays a crucial role in the economy of knowledge, though the extent and depth of this reliance have gone largely unrecognized in the philosophical tradition. He discusses those efforts that have been made to explain and justify the role of testimony in the getting and sustaining of knowledge or reliable belief, and concludes that, with the partial exception of Thomas Reid's discussion in the eighteenth century, they have been unsuccessful. This widespread failure, he argues, stems from a reductive approach with an individualist bias that fails to appreciate just how fundamental are our cognitive debts to one another. Indeed, he argues, the very possibility of linguistic communication rests upon some basic reliability of testimony. He spells out an alternative to the reductive way of understanding the links between testimony, perception, memory, and inference. In the latter part of the book, Coady explores several puzzles generated by our reliance on testimony, including those created by the tension between prior probabilities and testimony to astonishing events, the supposed increase in unreliability of testimonial chains of transmission as they expand, and a puzzle about competence and transmission of knowledge. He also discusses certain implications of his view of testimony for important issues in history, psychology, mathematics, and the law.