The lack of knowledge—as Timothy Williamson famously maintains—is ignorance. Radical sceptical arguments, at least in the tradition of Descartes, threaten universal ignorance. They do so by attempting to establish that we lack any knowledge, even if we can retain other kinds of epistemic standings, like epistemically justified belief. If understanding is a species of knowledge, then radical sceptical arguments threaten to rob us categorically of knowledge and understanding in one fell swoop by implying universal ignorance. If, however, understanding is not a species of knowledge, then three questions arise: (i) is ignorance the lack of understanding, even if understanding is not a species of knowledge? (ii) If not, what kind of state of int...