How should belief in God relate to evidence and argument? Thinkers have answered in very different ways, and believers themselves disagree.

Faith and reason in harmony

Many traditions hold that faith and reason work together. Thomas Aquinas taught that some truths about God, such as his existence, can be known by reason (natural theology), while others, such as the Trinity, are known only through revelation, and that sound reason and true faith cannot contradict each other. Similar views appear in Jewish thought, as in Maimonides, and in Islamic thought, as in Ibn Rushd, known in Europe as Averroes.

Pascal's wager

Blaise Pascal (1623 to 1662), a French mathematician and Catholic thinker, offered a different kind of argument in his Pensées, published after his death. He did not claim to prove that God exists. Instead he argued that, since reason cannot settle the question, we must consider what is wise to bet. If you wager on God and God exists, you gain an infinite good; if God does not exist, you lose little. If you wager against God and God exists, you lose infinitely. So the rational bet, given what is at stake, is on God. For those who cannot simply choose to believe, he recommended acting as believers do, until belief follows.

Replies: The many gods objection notes that many religions make rival claims, so which God should one bet on? Others ask whether God would reward belief adopted as a calculated bet, and whether we can believe at will at all.

Fideism and Kierkegaard

Fideism holds that religious faith does not depend on rational proof, and may go beyond it. The Danish thinker Søren Kierkegaard (1813 to 1855) is its most famous modern voice. He argued that faith is a passionate commitment, not an argument's conclusion. In Fear and Trembling (1843) he dwelt on Abraham's willingness to sacrifice Isaac, a story he found both terrifying and central to faith. Faith, for Kierkegaard, requires a leap (the phrase “leap of faith” is associated with him), and an objective proof would actually undermine the risk and inwardness that make faith what it is. He criticized comfortable, conventional religion as sharply as unbelief.

Critics worry that fideism cannot tell true faith from false, since any belief could be held by a leap. Defenders reply that much of what matters most in life, such as love and trust, also goes beyond proof.

Clifford versus James

In “The Ethics of Belief” (1877), the English mathematician W. K. Clifford told of a shipowner who sends an old ship to sea after talking himself out of his doubts; the ship sinks. Clifford argued the owner was guilty even had it arrived safely, because he had no right to his belief. His conclusion: “It is wrong always, everywhere, and for anyone, to believe anything upon insufficient evidence.”

William James answered in “The Will to Believe” (1896). Some choices, he argued, are genuine options: live, forced and momentous. When a genuine option cannot be settled by evidence, refusing to decide is itself a decision, and James held that our “passional nature” may lawfully decide. Waiting for proof might mean losing a great good, such as a friendship or faith, that comes only to those willing to commit. Critics say this licenses wishful thinking; defenders say James limited it to rare, genuine cases.

Belief without argument

Some recent philosophers argue that belief in God can be properly basic: reasonable without being based on argument, much as our belief in other minds or in the past is. Critics ask whether any belief at all could then claim the same status.

Worked example: Clifford, James and a hard choice

Rosa grew up in a religious family but now has serious doubts. She has read arguments on both sides and finds them roughly balanced. Should she keep practicing her faith, leave it, or simply wait? Consider how each thinker in this level might advise her.

Clifford would say: if the evidence is balanced, belief is not justified. Rosa should suspend judgment and keep investigating. Believing because it is comforting, or because her family expects it, would be like the shipowner silencing his doubts. Clifford would add that our beliefs affect others, so this is a moral matter, not just a private one.

James would ask whether Rosa faces a genuine option. Is belief live for her? Yes, it still feels possible. Forced? In a sense: not deciding means living without faith in practice. Momentous? Clearly, since it shapes her whole life. If so, and the evidence cannot settle it, James would say her passional nature may lawfully decide, in either direction.

Pascal would urge her to weigh what is at stake and, if she leans toward faith, to keep practicing, trusting that belief may follow practice.

Kierkegaard would say that no further reading will resolve the question for her. Faith is not a conclusion but a commitment of the whole self, and she must decide inwardly, fully aware of the risk.

Notice that none of these thinkers tells Rosa which way to decide; they disagree about how such a decision should be made. Notice too that a nonbeliever weighing whether to take up a faith could use exactly the same frameworks. The ethics of belief applies to everyone.