This chapter presents a detailed argument against a conception of self-knowledge that continues to dominate much of philosophical thinking today. It holds that we have an immediate and infallible access – a “privileged” access, as it is often termed – to the contents of our own minds. In reality, there does not exist any self-knowledge of this kind. The conception in question arises from a misunderstanding of the nature of the intimate relation that we bear to ourselves in virtue of which we are selves at all. A second central claim of this chapter is, then, that this essential relation we have to ourselves is not cognitive in character, but instead practical. It consists in our aligning ourselves on what appear to us to be pertinent reasons in all that we think and do. As a result, the self-knowledge that matters philosophically is not, as the Cartesian tradition has held, the supposedly first-person, immediate knowledge we have of our own mental states. Instead, the self-knowledge that truly matters is considerably difficult to achieve and is best understood along the lines of Plato’s ethics-centered idea of self-knowledge.