Faith and Proof: Can You Believe in Things You Can't Prove?

Dr. Timothy Keller opens the sermon by posing a practical problem: why do brilliant people like T.S. Eliot, Francis Collins, and Elizabeth Anscombe convert to Christianity, while equally brilliant people like Richard Dawkins and Bertrand Russell reject it? He proposes that the answer is not that one group is rational and the other is not, but that the process of gaining or losing faith is far more complex than most people are willing to admit.

Keller examines two popular but inadequate theories. The first holds that believers are rational while secular people are simply ignoring the evidence — but Keller rejects this because even the strongest arguments for God's existence are never completely airtight, and faith always requires more than reason alone. The second theory, dominant in places like New York City, claims that secular people rely on reason while religious people rely on faith and emotional need — but Keller draws on philosopher Charles Taylor to demonstrate that this is a mistaken 'subtraction story.'

Building on Charles Taylor's landmark work A Secular Age, Keller argues that secularism is not the absence of belief but a new set of equally unprovable beliefs. To live as though there is no God is itself an act of faith. Moreover, there are just as many emotional reasons to disbelieve in God as there are to believe, as philosophers Thomas Nagel and Aldous Huxley frankly admitted. Secular moral beliefs — including equal human rights and universal benevolence — cannot be proven scientifically and are themselves leaps of faith.

Keller develops a powerful argument from Friedrich Nietzsche: if the universe has no God and humanity arrived through evolution — the strong consuming the weak — then belief in equal human rights and universal benevolence is an even greater leap of faith than what Christians make. Secular thinkers such as John Gray and Andrew Koppelman themselves concede that modern secular humanism is a religious worldview with its own unresolved vulnerabilities and gaps.

The sermon closes with a practical call to action: rather than trying to prove one's belief system absolutely, listeners are invited to compare belief systems — examining whether they are internally consistent, whether they fit human experience, and whether they genuinely help a person face suffering, find meaning, and forge identity. Keller concludes with the biblical account of the father who cries out, 'I believe; help my unbelief,' reminding the audience that faith is a process and that what saves a person is not the quality of their faith but the object of their faith — Jesus Christ himself.