Is imagination a source of knowledge? Timothy Williamson has recently argued that our imaginative capacities can yield knowledge of a variety of matters, spanning from everyday practical matters to logic and set theory. Furthermore, imagination for Williamson plays a similar epistemic role in cognitive processes that we would traditionally classify as either a priori or a posteriori, which he takes to indicate that the distinction itself is shallow and epistemologically fruitless. In this chapter, I aim to defend the a priori-a posteriori distinction from Williamson’s challenge by questioning his account of imagination. I distinguish two notions of imagination at play in Williamson’s account – sensory vs. belief-like imagination – and show ...