Newton and Locke: the empirical spirit

The Enlightenment did not begin from nothing; it built on an inheritance from the Scientific Revolution of the seventeenth century. Two figures above all became its patron saints, and Voltaire’s Letters on the English (1733) canonized them for a French audience: Isaac Newton, who had explained nature, and John Locke, who had explained the mind. Together they supplied the movement’s physics and its philosophy.

Newton (1643–1727). In the Principia (1687), a single set of mathematical laws — three laws of motion plus universal gravitation — was shown to govern both the heavens and the earth: the same force that pulls an apple down holds the moon in orbit. Nature is orderly, lawful, and open to reason and observation — not to miracle, occult sympathy, or hidden qualities. See Mathematical Principles of Natural Philosophy.

Here is the leap the Enlightenment drew from Newton — and it is a leap. If the physical world yields to method and law, then perhaps everything does: morals, politics, and religion too might be studied with the same confidence, reduced to their own natural laws, freed from dogma and mystery. Newton became a license for a general program: a “Newton of the moral sciences” was the age’s recurring dream (Hume, among others, quietly hoped to be it).

Locke (1632–1704). If Newton is the Enlightenment’s physics, Locke is its epistemology and its politics in one man. In the Essay Concerning Human Understanding (1690) he argued against innate ideas: the mind at birth is a blank slate — tabula rasa — and all its contents are written by experience (sensation from without, reflection from within). This is empiricism: knowledge comes from experience, not stamped in advance. See An Essay Concerning Human Understanding II.i.

Locke’s reach went past the theory of knowledge. He argued for religious toleration (the state has no business coercing belief) and for government by consent — legitimate political authority rests on the agreement of the governed and exists to protect their life, liberty, and property. Epistemology and liberal politics, from one pen. That is why the Enlightenment adopted him so wholesale: he gave it both how we know and how we should be governed.

Put Newton and Locke together and you get the Enlightenment’s defining methodological shift. Away from grand a priori metaphysical systems — the seventeenth-century rationalist ambition to deduce all reality from first principles, as in Descartes, Spinoza, or Leibniz (The Monadology §7). Toward experience, observation, criticism, and utility. Knowledge should start from what we can observe, stay answerable to it, and prove its worth by being useful.

This empirical, anti-dogmatic, utility-minded spirit is the soil from which Kant’s critical philosophy will grow — and against which it will partly react. Kant inherits the demand that knowledge answer to experience and the refusal of dogmatic system-building; but, awakened by Hume’s skepticism, he will ask what the mind itself must contribute for experience to be possible at all. The Enlightenment’s empiricism sets Kant’s problem; his answer (Unit 4) both honours and transforms it.