---
title: Empiricism
sort: 130
section-id: epistemology
description: Locke, Berkeley, and Hume — the empiricist tradition and the limits of sensory knowledge.
language: en
---

# Empiricism

*Empiricism* is the epistemological view that knowledge derives from, and must be grounded in, sensory experience. Where rationalism privileges reason, empiricism insists that the mind at birth is a *tabula rasa* — a blank slate — and that all our concepts and knowledge are acquired through experience. The great British empiricists of the seventeenth and eighteenth centuries — John Locke, George Berkeley, and David Hume — explored this view with increasing rigour and found, perhaps to their own surprise, that it leads to deeply uncomfortable places.

## Locke's Empiricism

John Locke set the agenda for British empiricism in his *Essay Concerning Human Understanding* (1689). His starting point is a polemic against innate ideas: there are no ideas or principles inscribed in the mind from birth, contrary to what Descartes and Leibniz held ^[Locke, J., *Essay*, I.ii].

All ideas originate in experience, which Locke divides into two kinds: *sensation* (the senses providing ideas of external objects) and *reflection* (the mind observing its own operations — thinking, doubting, willing, perceiving). From simple ideas given in experience, the mind constructs *complex ideas* by combination, abstraction, and relation.

Locke's primary/secondary quality distinction (discussed in the previous chapter) is central to his epistemology. We have genuine knowledge only of relations among our own ideas; the extent to which our ideas correspond to mind-independent reality is limited to the primary qualities.

Locke's *Essay* is a monument of systematic empiricism, but it contains significant tensions. His account of substance — the "I know not what" that underlies the qualities we perceive — sits uneasily with his empiricism, since no experience corresponds to substance itself.

## Hume's Fork and Bundle Theory

David Hume pushed empiricism to its systematic conclusions with greater rigour and less embarrassment about where they led. In the *Treatise of Human Nature* (1739-40) and the *Enquiry Concerning Human Understanding* (1748), he developed what has been called the most powerful case in the history of philosophy for the limits of reason and knowledge.

*Hume's fork* divides all genuine claims to knowledge into two classes ^[Hume, D., *Enquiry*, §4]:

1. **Relations of ideas** — propositions knowable a priori by reason alone, whose denials are contradictions (mathematics, logic, conceptual truths). These are certain but tell us nothing about the actual world.

2. **Matters of fact** — propositions about the world, known a posteriori through experience. Their denials are conceivable. They are contingent and can only be known through experience.

Hume's criterion of empirical significance follows: any meaningful claim is either a relation of ideas or a matter of fact. Claims that fit neither category — much of traditional metaphysics, theology, and rationalist philosophy — are, famously, "nothing but sophistry and illusion" ^[Hume, D., *Enquiry*, §12.3].

On the self, Hume is radically deflationary. When he introspects, he finds no impression of a persistent, unified self — only "a bundle or collection of different perceptions, which succeed each other with inconceivable rapidity" ^[Hume, D., *Treatise*, I.iv.6]. The self, on his view, is a fiction constructed from the successive flow of impressions and ideas. Personal identity is a matter of psychological continuity, not a metaphysical substance.

## The Problem of Induction

Hume's most influential contribution to epistemology is his analysis of inductive inference. We routinely infer, from past regularities, what will happen in the future: the sun has risen every morning, so it will rise tomorrow. All known emeralds have been green, so the next emerald will be green. What justifies these inferences?

Not deductive reason: there is no logical contradiction in the sun's failing to rise. Not experience: to justify induction by appeal to the fact that induction has worked before is circular — it assumes the very principle in question ^[Hume, D., *Treatise*, I.iii.6].

Hume's conclusion: our habit of inductive inference is a psychological necessity — we cannot help forming expectations from regularities — but it has no rational justification. This is the *problem of induction*, sometimes called "Hume's guillotine" for the way it cuts off a seemingly obvious route to empirical knowledge.

The problem of induction has proved enormously productive. Karl Popper's falsificationism — the view that science proceeds by bold conjecture and attempted refutation rather than inductive generalisation — was an explicit response ^[Popper, K., *The Logic of Scientific Discovery*, 1934]. Nelson Goodman's "new riddle of induction" showed that the problem was deeper than Hume recognised: even if induction is sometimes reliable, we need a further principle to determine which regularities to project onto the future ^[Goodman, N., *Fact, Fiction and Forecast*, 1955].

## Hume on Causation

Hume's analysis of causation is equally influential. We believe that causes necessitate their effects — that fire *must* produce heat, that one billiard ball *must* move another when struck. But examining our impressions, Hume finds no impression of *necessary connection* between events ^[Hume, D., *Enquiry*, §7]. We observe constant conjunction — event A is always followed by event B — and we observe the spatial and temporal contiguity of cause and effect. But necessity itself is never observed.

Hume's account: the idea of necessary connection is a projection of our own psychological tendency to expect B after A, given repeated experience of their conjunction. The "necessary connection" is in us, not in the world.

This has generated enormous controversy. The *regularity theory* of causation — in Hume's footsteps — holds that causation just is constant conjunction (plus contiguity and temporal priority). Counterfactual theories, mechanistic theories, and probabilistic theories have all been proposed as improvements.

## Empiricism's Legacy

Empiricism as a systematic research programme continues in analytic philosophy. The logical empiricists (Carnap, Schlick, Neurath) developed a sophisticated version oriented toward the philosophy of science. Quine's naturalised epistemology — the view that epistemology is continuous with empirical psychology — is the most radical empiricist programme of the twentieth century ^[Quine, W.V.O., "Epistemology Naturalized", in *Ontological Relativity and Other Essays*, 1969].

The permanent contribution of the classical empiricists is methodological: the insistence that philosophical claims be answerable to experience, and the willingness to follow the logic of that insistence into uncomfortable territory.
