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 religious views with Aristotle's philosophical approach.
Whereas much of Aristotle's work was based on empirical observations of the physical, biological,
and social worlds, medieval discussions of Aristotle tended to treat his writings as a kind of sacred
text almost as venerable as the Bible or Koran.
Veneration of texts was challenged by the scientific revolution of the sixteenth and seventeenth
centuries. After the Royal Society of London was formed in 1660, its motto became “Nullius in
verba,” Latin for “nothing in words.” This phrase expressed the determination to base conclusions on
experimental methods such as those used by founding members Robert Boyle and Robert Hooke. Such
methods contrasted starkly with reliance on sacred religious and philosophical texts, although many
scientists, like Isaac Newton, remained religious. In the eighteenth century, however, the conflict
between science and religion became explicit in the writings of philosophers such as Voltaire and
David Hume. Today, most leading scientists are atheists or agnostics, either denying the existence of
God or expressing doubts about it. At the other extreme, religious fundamentalists in both the
Christian and Islamic traditions reject science as propounding views that are not just false but also
evil.
Some thinkers today attempt to reconcile science and religion, either by loosening religious
doctrines in ways that make them compatible with scientific findings, or by delegating different areas