2.5 Introduction to John Locke

What this lecture covers

This lecture introduces John Locke, the most influential philosophical figure of the 18th century and the first of the British empiricists (Locke, Berkeley, Hume). It builds on Boyle's corpuscularian theory from the previous lecture, since Locke adopted and extended Boyle's framework using his own terminology.

Millican explains what it means to call Locke an empiricist, distinguishing between deriving all ideas from experience and deriving all knowledge from experience, and shows how Locke's modesty about the limits of human knowledge shaped his views on substance, certainty, and probability. The lecture closes with Locke's controversial speculation that God could make matter think, and its connection to the still-unresolved problem of personal identity.

Key ideas

• Locke as empiricist: he held that all our ideas derive from experience, unlike Descartes, who thought some ideas (such as God and extension) are innate.
• Primary and secondary qualities: following Boyle, Locke distinguished primary qualities (shape, size, motion, solidity) from secondary qualities (color, taste and so on), which exist in bodies only as powers to produce ideas in us.
• Real essence versus nominal definition: Locke argued we cannot know the underlying 'real essence' of substances like gold, only their observable properties.
• Demonstration versus probability: demonstration yields infallible step-by-step certainty (as in mathematics), while most everyday reasoning yields only probable conclusions.
• A rationalist strand: despite being an empiricist, Locke suggested that perfect knowledge of microstructure would let us know behavior without experiment, and he offered a cosmological proof of God's existence.
• Thinking matter: Locke controversially speculated that although matter alone cannot think, an omnipotent God could give matter the power of thought, provoking accusations of impiety.
• Personal identity problem: because we cannot know the underlying essence of substances, including ourselves, Locke's framework raises unresolved questions about what makes someone the same person over time.

Walkthrough

Locke's life and influence (0:10)

The lecture opens with Locke's biography and his two major works, the Essay Concerning Human Understanding and the Two Treatises of Government, published shortly after his return to England around the Glorious Revolution of 1688.

Empiricist and Boylean framework (2:34)

Locke's adaptation of Boyle's corpuscularian theory is explained, along with the primary/secondary quality distinction and what it means to call Locke an empiricist about ideas and about knowledge, in contrast with Descartes's innate ideas.

Demonstration, probability, and a rationalist streak (7:24)

Locke's distinction between infallible demonstration and merely probable reasoning is introduced, followed by passages where Locke leans toward rationalism, including his suggestion that full knowledge of microstructure could yield certainty without experiment.

God, thinking matter, and personal identity (9:12)

The lecture closes with Locke's cosmological argument for God's existence, his controversial claim that God could make matter think, and the resulting problem of personal identity that this raises for later discussion.

Before you watch

• Watch lecture 2.3 on Robert Boyle first, since Locke's theory of matter and qualities builds directly on Boyle's corpuscularianism.
• Familiarity with lecture 2.2 on Hobbes helps, since the 'can matter think' debate responds directly to Hobbes's materialism.

Check your understanding

1. In what two distinct senses can Locke be called an empiricist?
2. How does Locke's distinction between primary and secondary qualities work?
3. Why does Locke think we cannot know the real essence of substances like gold?
4. Why was Locke's suggestion that God could make matter think so controversial?