The topic of this book is linguistic communication. More specifically, the topic is the nature of the sort of knowledge one acquires through accepting another speaker's say-so. My attraction to this topic derives from the prospect it holds for enabling one to bring together the three philosophical subfields I work in: philosophy of language, philosophy of mind, and epistemology. My core thesis is that a proper account of the nature of ‘testimonial’ knowledge (as it is called) will have us endorse anti-individualistic theses about language and mind, knowledge and justification.

My approach to the topic of testimonial knowledge can be described as ‘inter(sub)disciplinary.’ An overarching aim of the book is to illustrate the benefits of taking such an approach. But there are risks associated as well. Above all, there is the risk of superficiality in each of the relevant (sub)disciplines. I expose myself to this risk in the hope of bringing a unity that I have felt missing in other discussions of testimonial knowledge and linguistic communication. It goes without saying that in pursuing such a wide-ranging discussion I have been particularly dependent on the help and feedback of many others. I count myself unusually fortunate in the indulgence shown to me by teachers, colleagues, and friends, as I talked about – OK, obsessed over – the nature of the testimonial exchange. This book has been shaped by many conversations, over many years, with more people than I can remember.