<p>People often tell us about their thoughts, feelings, and desires. This common practice has led some philosophers to claim that testimony is a fundamental way of knowing about others’ minds, a way of knowing that does not epistemically depend on any other way of knowing. In this essay, I shall argue that this view is plausible only if we assume a conception of testimony that aligns it with perception. By contrast, I shall argue that if we adopt a conception of testimony as a type of assurance, then testimonial knowledge would epistemically depend upon our having some non-testimonial knowledge of others’ mental states. More specifically, I shall argue, it would epistemically depend on knowledge based on expressive behaviour. Although one might naturally think this knowledge is either perceptual or inferential, I shall develop an alternative framework for explaining how expressions of mental states secure knowledge of others’ minds.</p>