The thesis developed and defended in this paper is that is it false that all knowledge is founded on experience. Much of our knowledge (or alleged knowledge), it is argued, is based on testimony. Still, many philosophers have either not dealt with testimony at all, or treated it very unkindly. One of the reasons for this is that those philosophers (such as Descartes and Locke) work with a concept of knowledge according to which knowledge is certain, indubitable, and/or self-evident. And (...) if knowledge is what these philosophers say it is, then there is no such thing as knowledge based on testimony indeed. Thomas Reid is introduced as holding that we do have testimonial knowledge and that therefore Descartes’ and Locke’s concept of knowledge is untenable. Reid furthermore holds that human beings are endowed with a disposition to accept or believe what otherstell us („the principle of credulity”). The working of this principle is refined through all kinds of experience. What Reid says or shows is how this disposition in fact operates. Many epistemologists, however, have higher aspirations and look for reasons or arguments that can justify our factual acceptance of testimony. The inductive argument Hume offers, it is argued, is unconvincing. There is even reason to think that the principle of credulity can never be justified by adducing reasons. This does not imply, however, that acceptance of testimony is unjustified. Whether or not it is depends, among other things, on the concept of justification one uses. On an internalist concept of justification (as Locke’s or Hume’s) this disposition may never be justified. But on an externalist conception it may. This may be disappointing, given some widely held philosophical aspirations, but at the same time it is, as Alston has said, a lesson in intellectual humility. (shrink)