Nova: Here's a puzzle that has haunted religion for centuries. Some of the most passionate defenders of faith have argued that faith's best friend is actually doubt. That the more you tear down human reason, the stronger faith becomes. Sounds backwards, right? Well, one philosopher spent an entire book deciding whether that idea is brilliant or a disaster.

Nova: Terence Penelhum, a British-Canadian thinker who spent decades at the University of Calgary. His 1983 book is called God and Skepticism, and its closing chapter, the one people still argue about, is called The Nature of Faith. And here's the twist: Penelhum thinks the whole let's-destroy-reason-to-help-faith project gets faith exactly backwards.

Nova: Think of it this way. A skeptic normally says, we can't know anything for sure. A believer says, I'm committed with my whole life. Those look like opposites. Yet Penelhum traces a long tradition, running from the sixteenth and seventeenth centuries up to his own day, of Christian thinkers who used skeptical arguments to defend faith. His mission is to show that this alliance is a bad deal for faith.

Nova: What's at stake is what faith actually is. Is it a set of beliefs you're certain about? Is it a feeling? Is it trust? Because if we get that wrong, we misunderstand the whole thing. And Penelhum's answer, that faith is trust before it is belief, might change how you see the religious life, and even ordinary human relationships.

Nova: Let's start with the label Penelhum uses for this strange alliance: skeptical fideism. Fideism is the view that faith needs no support from reason. A skeptical fideist goes further and says reason is powerless in general, and that this is somehow good news for faith.

Nova: Penelhum says it comes in two main flavors. First, the conformist skeptical fideists, like Montaigne and Bayle. They accept the ancient Pyrrhonian recipe: suspend judgment, cultivate quiet, and simply conform to the customs and faith of your community. Bayle even argued that Christianity is inconsistent with what reason delivers.

Nova: That's almost exactly Penelhum's word. He calls that version of faith tepid. It is so mild it hardly deserves the name faith at all, especially within Christianity, which demands a passionate, whole-life commitment.

Nova: The evangelical skeptical fideists, exemplified by Pascal and Kierkegaard. They accept the skeptical diagnosis that reason is feeble, but they reject the quiet cure. They say suspension of judgment isn't really possible. We can't stop believing common sense even when we can't prove it. And the despair the skeptic induces needs an answer: passionate, committed, rationally unsupported faith.

Nova: It does, and Penelhum takes it seriously. But he still rejects it. His core objection is this: if the skeptic is right that reason is powerless, then it becomes less likely, not more likely, that unbelief is caused by human corruption, which is what the evangelicals blame. And if faith's claims are actually sound, then natural theologians trying to support those claims with reasons cannot be dismissed as hindrances.

Nova: That's the heart of it. Penelhum thinks skepticism doesn't clear the ground for faith. It poisons the ground. But he's careful. He doesn't throw out every version of a key argument these thinkers use. That argument has a name, the parity argument, and it's our next stop.

Nova: The parity argument goes something like this. Religious beliefs and common sense beliefs are equally unsupported by reason. But we accept our common sense beliefs anyway, and we can't really reject them. So, the argument concludes, we should equally accept religious belief.

Nova: Exactly. Penelhum traces several versions. The conformist version says all beliefs are equally unjustified, so suspend judgment and just follow custom. The evangelical version says common sense and belief in God are both faith beliefs, so it's inconsistent to accept one while rejecting the other.

Nova: He finds several cracks. First, the evangelicals haven't actually ruled out the conformist's tepid response. Second, there's a real difference: common sense beliefs are extremely hard to resist, but religious beliefs apparently aren't, since people abandon them all the time. Third, parity doesn't favor one religion over another. And fourth, you can argue against the parity itself.

Nova: Yes, and this is where Penelhum shines as a lifelong Hume scholar. He reads Hume as recognizing that he's vulnerable to the parity argument, then building three defenses against it.

Nova: First, Hume says religious belief is pathological. It isn't natural and instinctive like common sense. It originates in fear, it can be dislodged, and it gets in the way of science. Second, even if the parity argument works, it only gets you a vague deism, not Christianity. And third, Hume accepts that vague deism and becomes a conformist fideist, going along with the religion of his culture.

Nova: Exactly. Penelhum is sympathetic there. And notice something important: after all this criticism, he doesn't reject everything. He accepts a weaker, permissive version of the parity argument, drawing on Alvin Plantinga and Norman Malcolm.

Nova: Right. The permissive version doesn't say belief in God is required or proven. It says religious belief is rationally permissible, meaning believers can at least be defended against the charge of being irrational. That's a much humbler claim, and Penelhum thinks it stands.

Nova: The payoff is his most quoted line: trust, rather than belief, is the essence of faith. But, and this is crucial, trust has to rest on certain beliefs about the person you're trusting.

Nova: Exactly. If I trust a doctor, I believe she's competent and honest. Trust isn't belief-free. It's built on belief. Penelhum says the same about faith in God. And this is precisely why he takes issue with Thomas Aquinas.

Nova: Aquinas famously places faith midway between knowledge and opinion. Faith carries conviction like knowledge, but it's about things we don't see directly. Penelhum thinks Aquinas makes belief the essence of faith, the intellectual assent to propositions, and he thinks that's a mistake. It misses the trusting, relational core.

Nova: That's the shift. And Penelhum engages another voice here: Wilfred Cantwell Smith's 1979 book Faith and Belief. Smith wanted to sharply separate faith and belief, with faith as personal trust and belief as mere propositional assent. Penelhum appreciates Smith's learning but can't accept that sharp separation, because trust requires beliefs about the trusted person.

Nova: Perfect. And Penelhum also draws on Richard Swinburne's 1981 book Faith and Reason to sharpen this. Swinburne connects faith to trust and to how we assess evidence about God's existence and goodness.

Nova: That's a beautiful summary. But there's one more target he takes down before he's done, and it's the Wittgensteinian view.