Don't let anyone tell you that philosophy is useless. True, it has a reputation for being an abstract and chronically inconclusive enterprise. But "applied" forms of philosophy like medical ethics and business ethics have enjoyed a boom in recent times, and in earlier periods philosophy was also applied in eminently practical contexts. Actually medicine is a good example. Galen, the second century AD author whose writings were nearly synonymous with medical science for well over a millenium in Europe and the Islamic world, appropriated ideas from ancient natural philosophy in his humoral theory and pharmacology. Another example is the study of the heavens. The cosmological theories of Aristotle provided a theoretical basis for Ptolemy, who lived at about the same time as Galen, and whose writings about both astronomy and astrology were widely influential in medieval culture. This sounds less practical at first, but actually astrology--known through texts from both Greece and India--was one of the main topics pursued in the Arabic translation movement, again for eminently practical reasons.

What, after all, could be more useful than using the stars to predict the future? Many people nowadays think of philosophy and religion as being antithetical, with philosophy devoted solely to reason and religion founded in faith. But in the medieval period, religious thought was frequently just another kind of applied philosophy. Ideas about knowledge, metaphysics, or the soul would be appropriated and used to interpret, expound, and defend revelation. Indeed we've already seen that Averroes, for one, thought that philosophy provided the only reliable basis for scriptural exegesis. Obviously this was not a widely held view, and there were certainly some medieval theologians who were frankly hostile to the use of philosophy in religious contexts, going all the way back to the early Christian church father Tertullian, who famously wanted to know what Athens has to do with Jerusalem. Examples from our three medieval cultures might include Ibn Taymiyya (d.1328), who very unusually went so far as to reject the study of logic, which he deemed more trouble than it was worth (like "camel meat at the top of a mountain"); Bernard of Clairvaux (d.1153), who justified the intellectual persecution of Peter Abelard by complaining that Abelard was "ready to give reasons for everything, even for those those things which are above reason"; and Symeon the New Theologian (d.

1022), a monk at the Stoudios monastery in Constanstinople who acidly remarked that the Holy Spirit is "not sent to philosophers. but to the pure in heart and body." But in this chapter, I will be looking at figures who had a more nuanced view, one that falls between the bold rationalism of an Averroes and the invective of these outright critics of philosophy (who, by the way, also left plenty of space for rationality within their own approaches to religion). On the one hand these middle-ground figures perceived the philosophical tradition as a kind of rival, or at least alternative, to religious faith. On the other hand they believed that natural reason could be used to support religious faith and even to justify one's religious affiliation. I'll be focusing on several works written in dialogue form, which explore the choice between religions by putting them in literal debate with one another. Tellingly, "philosophy" tends to appear in these dialogues as another option on a par with Islam, Judaism, and Christianity. The central claim made by such texts is, therefore, that the neutral and fair-minded person who is simply using natural reason should give credence to one of the Abrahamic faiths.

By arguing for this conclusion, they suggest that reason points beyond itself, establishing the need for a religious revelation that supplements our natural understanding of the world and of our own obligations.