Rationalism

The core idea

The great continental rationalists, René Descartes, Baruch Spinoza and Gottfried Wilhelm Leibniz, held that the mind has access to truths that do not come from experience, such as those of mathematics and some of metaphysics. Some ideas, they argued, are innate, and reason can build on them to prove substantial truths about God, the mind and the world.

Their model of knowledge was geometry: start from self-evident principles and proceed by strict demonstration. Spinoza wrote his Ethics in exactly this form. Leibniz's principle of sufficient reason is a characteristic rationalist commitment: the world must be fully intelligible to reason.

The modern contrast between rationalism and empiricism is partly a later simplification, but it captures a real disagreement about the sources and limits of knowledge.

What they hold

• Some knowledge is A priori and a posteriori, independent of experience.
• Some ideas or principles are innate rather than learned.
• Reason can establish truths about the nature of reality.
• Everything has an explanation that reason can, in principle, grasp.

The main criticisms

Empiricists such as John Locke and David Hume denied that there are innate ideas and argued that reason alone can tell us only about the relations between our ideas, not about matters of fact. Immanuel Kant tried to show that both sides were partly right.

Further reading

• EncyclopediaStanford Encyclopedia of Philosophy: Rationalism vs. Empiricism
• WikipediaRationalism