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Compared

Humean empiricism and skepticism versus Rationalism

Both are theories of where knowledge comes from. Rationalists trust reason to reach truths on its own. Hume held that every idea comes from experience, and that reason cannot justify much beyond it.

What they share

Both are theories about where knowledge comes from, and both treat mathematics as secure. Hume accepts that truths about relations between ideas, such as 2 + 2 = 4, are known independently of experience and with certainty.

Where they differ

  • The source of ideas. Rationalists such as Descartes, Spinoza and Leibniz held that knowledge has its foundation in the mind's own principles, and all three accepted some form of innate ideas. Hume held that all simple ideas are copies of impressions, so the mind starts with nothing of its own.
  • How far reason reaches. Rationalists modelled philosophy on geometry: start from self-evident principles and deduce, and pure inference can reach certain knowledge. Hume argued that reason cannot justify our expectations about the unobserved or our idea of a necessary connection between cause and effect. These come from custom and habit.
  • Ethics. Rationalists held that moral truths can be reached by reason alone. Hume held that moral distinctions come from sentiment, and that reason by itself does not move us to act.

A question that separates them

  • Where does knowledge come from? “Careful thinking alone can reach real truths about the world” against “What we know comes from experience, and pure thinking cannot prove big claims”.
  • How certain can we be? “Some things can be known for certain by reason” against “Certainty is rare, even about everyday things”.

“Rationalist” and “empiricist” are labels applied afterwards, and most thinkers of the time held mixed views. This page compares the usual picture of the two groups, with Hume as the empiricist case.

Written by epchē in our own words, and checked against independent sources on 8 October 2026. The sources are listed below.

Read each on its own

Sources we used

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