Chapter Two evidence beats faith Faith versus Evidence When you have a medical problem, where do you look for information that might help you deal with it? Perhaps you consult a medical expert such as your family doctor, or maybe you go looking on the Web to see what practitioners of alternative medicine have to say about it. Or else you might ask a religious leader to whom you look for medical as well as spiritual guidance. My preference in medicine as well as philosophy is to look for scientific evidence rather than religious faith or a priori reasoning, but what justifies this preference? Isn't it just a matter of having faith in science rather than in religion? No: this chapter will provide good reasons for basing beliefs and decisions on evidence rather than on faith. After a brief history of the conflict between scientific evidence and religious faith, I will describe how faith and evidence differ in the way they affect beliefs and decisions. I will use medicine as an informative area in which the superiority of evidence over faith is clear, and generalize this superiority to other domains, including philosophy. Although the tradition of a priori reasoning in philosophy is not usually allied with religious faith, I will argue that its reliance on intuitions and neglect of evidence is similar to faith-based thinking. The currently common use of thought experiments in philosophy is akin to reasoning based on faith rather than on evidence. Plato and Aristotle, long the most influential philosophers, saw no deep conflict between reason and religion. Both included theology as a crucial part of their thinking about the nature of reality and morality. They differed in that Plato argued for the superiority of a priori knowledge based on abstract ideas, whereas Aristotle's approach was more empirical, drawing much more on what was known at the time about the physical and biological worlds. Medieval philosophers in various religious traditions—Averroes for Islam, Maimonides for Judaism, and Thomas Aquinas for Christianity—attempted to integrate their