I focus on two questions: what is knowledge, and how is knowledge possible? The latter is an example of a how-possible question. I argue that how-possible questions are obstacle-dependent and that they need to be dealt with at three different levels, the level of means, of obstacle-removal, and of enabling conditions. At the first of these levels the possibility of knowledge is accounted for by identifying means of knowing, and I argue that the identification of such means also contributes to (...) a proper understanding of what knowledge is. (shrink)