Anyone taking a class in Modern Philosophy will learn that one of the most important issues in 17th and 18th Century philosophy was the debate between rationalists and empiricists. In 2005, Matthias Steup and Ernest Sosa edited a book entitled Contemporary Debates In Epistemology (Oxford: Basil Blackwell, 2007), which includes a chapter entitled ‘Is There A Priori Knowledge?’ (pp. 98–122). In this chapter, Laurence BonJour defends rationalism and Michael Devitt defends empiricism. So, this philosophical debate has been going on for four centuries, and it still has not been settled. This is the kind of thing that gets philosophy a bad reputation. If a dispute can continue for four centuries without resolution, that is surely an indication that nobody knows how to tell a good answer from a bad one. In this article I want to consider why the debate is unresolved after so much time.