Knowledge as a concept has been a central concern of human curiosity as far back as we have records of people’s thoughts. What counts as knowledge and what kinds of criteria we can use to establish knowledge, provide the fulcrum for intellectual life. The answers must be inevitably related to the particular world view of a culture and the first part of this article will deal with some of the issues and ways in which they have been dealt with by philosophers in the Western tradition. Subsequent to this discussion of knowledge in general terms, the special case of self-knowledge will be discussed in relation to its correlate, self-deception. As will be shown initially, the viability of mistakes only makes sense if we allow for the possibility of knowledge. So, for individuals, their knowledge of the outside world must always be referential to their knowledge of themselves. How much of this knowledge is tolerable and manageable and therefore how far it is desirable will be seen in relation to this overall thesis.