Descartes, Hume, and the Rationalist–Empiricist Debate on God

Introduction: Two Paths to Proving God

The question of how — or whether — the existence of God can be proven has occupied philosophers for centuries. Two major traditions offer competing answers: rationalism, which grounds knowledge in the structures of the mind, and empiricism, which grounds knowledge in sensory experience and observation. Examining these approaches side by side reveals not only their differences but also, perhaps surprisingly, a shared vulnerability.

Descartes and the Rationalist Case for God

The philosopher René Descartes can be regarded as the supreme rationalist. Descartes believed that only through our rational minds could we fully know God and find evidence of God's existence. Empirical knowledge was not sufficient justification, because our senses could delude us or prove faulty — through madness or blindness, for example. Through rational inquiry, by contrast, we could first demonstrate our own existence on a mental plane: even if everything concerning the body is a delusion, there must be some mind doing the thinking, as Descartes reasoned. And because the human mind can conceive of a greater intelligence — God, a level of perfection human beings cannot approach — the very structure of our mind contains evidence of God.

Hume's Dialogues and the Empiricist Challenge

David Hume's Dialogues Concerning Natural Religion takes the opposite, empiricist point of view. In the dialogue, three figures — Demea, Cleanthes, and Philo — engage in a debate over how, and whether, God can be proven to exist. Cleanthes, in opposition to Demea and the Cartesian point of view, believes that the perfect, mechanical workings of the world demonstrate that some overriding intelligence must be at hand in the creation: "You will find it to be nothing but one great machine…therefore, the effects resemble each other, we are led to infer, by all the rules of analogy, that the causes also resemble; and that the Author of Nature is somewhat similar to the mind of man, though possessed of much larger faculties, proportioned to the grandeur of the work which he has executed" (Hume 143).

Philo, in contrast, is an absolute skeptic. He observes: "Nothing exists without a cause; and the original cause of this universe (whatever it be) we call God; and piously ascribe to him every species of perfection" (Hume 142). For Philo, however, this attribution is the product of mental gymnastics, not of any genuine causal connections that actually obtain in the world.

Conclusion: Analogy, Bias, and the Bounds of Human Inquiry

Although such superstitions are no longer in common currency, the act of stereotyping someone based upon past experiences — assuming that membership in a different racial or ethnic group causes particular behaviors — likewise illustrates the faulty nature of pure empiricism and inductive reasoning. The analogy between the apparent intelligent design of a watch made by a human hand and the hand of God in the universe is simply too great an intellectual leap for critics of empiricism such as Philo. As Hume writes: "The exact similarity of the cases gives us a perfect assurance of a similar event; and a stronger evidence is never desired nor sought after. But wherever you depart, in the least, from the similarity of the cases, you diminish proportionably the evidence; and may at last bring it to a very weak analogy, which is confessedly liable to error and uncertainty" (Hume 144). In the end, both rationalism and empiricism, when applied to the question of God's existence, run up against the boundaries of what human cognition can reliably establish.