This chapter examines the relation of logic to method and knowledge. Let us first consider that of logic to method. Method is a means of solving problems, thus a means of discovery. There are various kinds of methods, but an important distinction is that between algorithmic and heuristic methods. While algorithmic methods guarantee to solve problems, heuristic methods do not guarantee that, but may serve as a guide towards that end. The formal literature on heuristics tends to suggest that the purpose of heuristics is to formulate mechanical rules that can be programmed on a computer. But this is misleading because the purpose of heuristics is rather to find non-mechanical rules that will guide one to solve problems, even if it takes some skill to apply them.