3.1 Introduction to David Hume

What this lecture covers

This lecture closes the course's historical survey and opens its first main topic: induction. Millican introduces David Hume as, in his view, the greatest philosopher of the early modern period, and explains how Hume builds on Newton and Locke by giving up on the idea that science can deliver ultimate understanding rather than mere systematic description.

You'll come away able to state Hume's billiard-ball thought experiment, explain why he thinks reasoning from past to future experience cannot be rationally justified, and see how this skepticism about induction extends to human reason, free will and morality.

Key ideas

• Systematization over understanding: following Newton, Hume holds that science gives formulas that describe how things behave, not insight into why they behave that way.
• The billiard-ball thought experiment: a newly created Adam watching one ball strike another could not predict the outcome, because he has no prior experience to draw on.
• The problem of induction: past experience only justifies predictions about the future if we assume the future will resemble the past, and that assumption cannot itself be proven by logic or by further experience without circularity.
• Habit, not insight: Hume compares human reliance on causal expectation to a dog's habit of associating the lead with a walk, denying that either rests on rational insight.
• Compatibilism about free will: Hume follows Hobbes in treating free will as consistent with determinism, defining it as simply the power to act as one's will dictates.
• Morality grounded in sentiment: rather than basing ethics on pure reason, Hume roots it in natural fellow feeling and empathy for others.
• The 'elephant in the room': Millican stresses that religious concerns underlie nearly all early modern philosophy, even when not stated openly.

Walkthrough

Hume's life and works (0:10)

Millican gives brief biographical context: Hume lived from 1711 to 1776, wrote the Treatise of Human Nature in 1739, and later published influential essays, a history of England, and the posthumous Dialogues Concerning Natural Religion. He frames Hume as building on Newton's instrumentalism and Locke's rejection of certainty in science.

The billiard balls and induction (2:12)

Using the billiard-ball case, Millican walks through why Hume denies that mechanical causation is any more intelligible than gravity. He then develops the core argument: expecting future collisions to follow past patterns requires a justification for extrapolating from past to future, and no such justification is available from logic or from experience itself, since appealing to experience to justify trusting experience is circular.

Human reason as animal instinct (7:14)

Hume's skeptical conclusion is that scientific expectation rests on a "brute animal instinct" rather than rational insight, illustrated by the analogy of a dog's habitual anticipation. Millican connects this to the period's religious self-image of humans as reflecting God's reason, and notes how Hume's picture instead places humans within the natural, animal world—a lesson he suggests modern economists' assumptions of perfect rationality could still learn from.

Free will and morality (10:18)

Millican explains Hume's compatibilism: human action is causally determined like the billiard balls, yet free will is simply the ability to act as one wills. He then covers how Hume grounds morality not in reason but in sentiment and empathy, arising from natural fellow feeling rather than pure calculation.

The bigger picture of the crisis (12:20)

The lecture ends by tying Hume's views back to the course's recurring theme: an early modern "crisis" in physics, morality and politics caused by the collapse of medieval certainties about natural motion, revealed morality and divine authority, replaced by mechanistic causation, contested moral foundations and contested political authority. Millican previews how these tensions—skepticism, mind and body, personal identity—will recur throughout the course.

Before you watch

• Review the previous lecture's treatment of Newton's instrumentalism and Locke's rejection of certainty, since Hume is presented as extending both.
• Be ready to encounter the term "induction" used in its philosophical sense: inference from observed cases to unobserved or future ones.

Check your understanding

1. Why does Hume think that even Adam, with perfect reasoning ability but no experience, could not predict the outcome of one billiard ball striking another?
2. What is circular about trying to justify induction by appealing to past experience?
3. How does Hume's compatibilism attempt to reconcile free will with causal determinism?
4. In what way does Hume ground morality in sentiment rather than reason, according to the lecture?