Searching for skepticism in medieval philosophy seems to be a vain enterprise, because no philosopher in the Christian tradition radically doubted or even denied the possibility that human beings can have knowledge. Nor did thinkers in the Jewish or Islamic tradition categorically refute the claim that human knowledge is possible, despite their criticisms of the incompleteness and fallibility of our cognitive faculties. All of them agreed that our faculties enable us to acquire a wide range of knowledge – of material things as well as of mental, mathematical, and other intelligible objects. Their main concern was not to establish that we can have knowledge but to explain how, that is, by what kind of cognitive mechanism, we are able to acquire it. There is no evidence that they were interested in Pyrrhonism, one of the main forms of ancient skepticism that aimed to show how one can reach “mental tranquility” and a happy life by suspending all beliefs. Although a Latin translation of Sextus Empiricus’s Outlines of Pyrrhonism was available before 1300, this key text had no visible impact on debates in Western Europe. All philosophers in the Latin tradition subscribed to the thesis that we are entitled to have beliefs; they even claimed that we need beliefs to choose specific actions and to pursue a happy life. Thanks to Cicero’s Academica and Augustine’s Contra academicos, Academic skepticism, the second major form of ancient skepticism, was to some extent known during the Middle Ages. But it did not spark an extensive debate or a “skeptical crisis.” Medieval authors in the Latin West occasionally referred to skeptical arguments and examples presented in these texts (such as cases of sensory illusions and dream experiences), but without drawing radical skeptical conclusions.