Empiricism

John Locke opened the empiricist tradition by attacking the idea that the mind arrives already furnished with innate principles, arguing instead that the mind at birth is a blank tablet on which experience, through sensation and reflection, writes everything it will ever contain. George Berkeley pushed the same premise toward a radical conclusion: if all we ever really have access to are our own ideas, then talk of a mind independent material world sustaining those ideas is talk we cannot justify, and what keeps the world in existence when no finite mind perceives it is the mind of God perceiving everything continuously.

David Hume pushed empiricist premises harder still and did not arrive at Berkeley's comforting conclusion. Hume argued that what we call cause and effect is never something we actually observe, only a constant conjunction of one event following another that habit trains us to expect, which leaves the traditional design argument for God, reasoning from the world's order to an intelligent designer, resting on an inference experience cannot deliver. His argument on miracles held still more bluntly that no testimony could ever make it more probable that a law of nature was violated than that the witness was mistaken or lying, since a violation of nature is by definition the least probable explanation available. This atlas states Hume's conclusions as he drew them rather than softening them: empiricism did not set out to be religion's rival, but followed to its own strict standard of evidence, it became one.

Locke's argument in A Letter Concerning Toleration draws directly on the empiricist epistemology he had just finished defending in the Essay Concerning Human Understanding: since no one's mind arrives certain of contested metaphysical truths, and coercion cannot in any case produce genuine inward belief, only persuasion by evidence and argument, the very method the Essay recommends, can rightly move a mind toward true religion, so civil punishment for wrong belief is both illegitimate and useless. Locke excluded Catholics, on the ground that loyalty to a foreign sovereign made political rather than religious sense to police, and atheists, on the ground that a promise sworn by someone who does not believe an oath is binding before God carries no real force, exclusions later readers have treated as the theory failing its own premises rather than as incidental detail. The argument nonetheless became one of the empiricist tradition's most consequential exports into practical politics: it supplied much of the vocabulary the framers of religious liberty clauses in the American colonies and, later, the United States Constitution drew on, translating a claim about the limits of what the mind can know into a claim about the limits of what the state may compel.