So Henry’s arguments, far from showing that certainty is possible through divine illumination, actually lead to a pervasive skepticism. Scotus counters that we can show that skepticism is false. We can in fact attain certainty, and we can do so by the unaided exercise of our natural intellectual powers. There are four types of knowledge in which infallible certainty is possible. First, knowledge of first principles is certain because the intellect has only to form such judgments to see that they