Keller, discussing William Kingdon Clifford’s famous essay “The Ethics of Belief”, espousing exclusive rationality:
[F]ew of our convictions about truth can be proven scientifically. While we may be able to demonstrably prove to any rational person that substance X will boil at temperature Y at elevation Z, we cannot so prove what we believe about justice and human rights, or that people are all equal in dignity and worth, or what we think is good and evil human behavior. If we used the same standard of evidence on our other beliefs that many secular people use to reject belief in God, no one would be able to justify much of anything. The only things that would be “ethical” to believe in would be things that could be proven in a laboratory. Philosopher Peter van Inwagen points out that the Clifford essay is often assigned in religion classes today but never in classes on epistemology (which addresses how we know what we know). That is because, Van Inwagen says, there are almost no teachers of philosophy in the West who believe in Clifford’s view of reason anymore.
— Making Sense of God: An Invitation to the Skeptical