Empiricism: The British Tradition of Experience-Based Knowledge

The Leviathan was published in 1651, the year England hanged its king. The book made Thomas Hobbes, then sixty-three, the most dangerous intellectual in Europe. Its central claim — that there are no incorporeal substances, that the mind is a complex of motions in the brain caused by the impact of external objects on the sense organs, that all knowledge is derived from sensation — was not what its readers expected from a royalist defending Charles I’s memory. But Hobbes was, in fact, the founding figure of the British empiricist tradition, and the most underrated one. He did not get to keep his head; the title of his book has become a synonym for an all-powerful state. That is the way the history of philosophy occasionally distributes its larcenies.

Empiricism is the tradition that holds that all knowledge derives from experience. The claim sounds modest, almost banal, in the twenty-first century. In the seventeenth and eighteenth centuries, it was anything but. It implied a repudiation of the Aristotelian-scholastic picture of knowledge as the recognition of eternal essences through reason; it implied a new method for the natural sciences; it implied a new account of the human mind; and — as Hobbes was the first to see — it had political consequences, since if there are no innate ideas then there are no natural hierarchies written into the structure of the universe.

The seventeenth-century groundwork: Bacon and Hobbes

Francis Bacon (1561–1626) is usually given the title of “father of empiricism,” and the title is not entirely wrong, although it can be misleading. Bacon’s Novum Organum of 1620 set out a new method of natural philosophy based on the gradual accumulation of natural facts and the inductive inference of general conclusions. He called the scholastic method a “web” of abstractions and called for a return to direct encounter with the natural world. The Royal Society, founded in 1660, took him as its patron saint.

But Bacon’s empiricism was, in a sense, the cheerful version. He thought that careful observation would eventually disclose the real structure of nature, and he did not subject the categories of observation to a serious skeptical examination. That is the harder version, and it was Hobbes who began it.

Hobbes (1588–1679) was Bacon’s secretary in the 1620s, and he was decisively influenced by the older man’s program. But Hobbes pushed the empiricist premises in a direction Bacon had not anticipated. The Leviathan and De Corpore (1655) developed a materialist account of the mind: there are no incorporeal substances; mental events are motions in the brain; the so-called ideas of the mind are the residue of sense impressions. This was a reductionist program, and it was politically explosive. If all knowledge derives from sensation, then there is no foundation in the structure of the universe for natural rights, natural hierarchies, or natural laws anterior to the establishment of political authority. Sovereignty is artificial; it is what we make of it; and we make it by mutual agreement, in order to escape the state of nature, which Hobbes described as “solitary, poor, nasty, brutish, and short.”

The phrase has been quoted out of context for three hundred years. It is worth pausing on. Hobbes was not claiming that pre-political human life had been historically like that — he was making a logical point about what life would be like in the absence of a sovereign. The point was not anthropological but analytic: remove the state, and the rest follows. The political implication was that political authority is conventional, and that the only proper basis for it is the consent of the governed. The Royalist Hobbes, defending absolute sovereignty, ended up laying the foundations for the modern theory of legitimate authority. The history of political philosophy is not kind to the irony.

John Locke and the Essay

John Locke (1632–1704) is the figure most people mean when they say “empiricism.” His Essay Concerning Human Understanding (1689) is the foundational text of the modern empiricist tradition, and it is the book that set the terms of philosophical debate in Britain and France for the next two centuries. Locke’s Essay is, in addition, the kind of book that almost never gets written now: a four-book philosophical treatise, in clear prose, with a complete theory of perception, language, knowledge, and the limits of human understanding, written by a man who had spent twenty years thinking about it and who was not in a hurry.

The famous image is the tabula rasa, the blank slate. The mind, Locke argued, is not born with innate ideas. It begins as a piece of paper with no writing on it. All the materials of knowledge are derived from two sources: sensation, which gives us ideas of the external world (colors, sounds, shapes, textures), and reflection, which gives us ideas of our own mental operations (thinking, willing, doubting, believing). The mind then combines, compares, and abstracts these materials in various ways to construct the more complex ideas of the sort we have of triangles, gold, identity, causation, and God.

The distinction between primary and secondary qualities was, in its day, the most influential part of the book. Primary qualities — solidity, extension, figure, motion, number — are properties that the object has “in itself,” and that produce the same ideas in all observers. Secondary qualities — color, sound, taste, smell — are not properties of the object itself, but powers of the object to produce certain ideas in observers by virtue of its primary qualities. The chalk is white, but the whiteness is in the interaction between the chalk and the visual system, not in the chalk alone. The distinction is the philosophical ancestor of every modern account of perceptual relativity, and it was developed in detail in Book II of the Essay.

The Essay is a remarkably generous book. Locke canvasses opinions he disagrees with; he marks off the limits of human knowledge with care; he includes a chapter on the “association of ideas” that anticipates, in its general shape, the entire tradition of associationist psychology. He is also, philosophically, the softest of the major empiricists. He believes, in the end, that we can have knowledge of the existence of God, knowledge of our own existence, and some knowledge of the external world. He is not a skeptic. The skeptic in the tradition is the next major figure, and the difference between them is the whole distance between the moderate and the radical Enlightenment.

George Berkeley and the immaterialist turn

George Berkeley (1685–1753), an Irishman, a mathematician, and a bishop, took the empiricist program at its word and pushed it in a direction that Locke had not anticipated. Berkeley’s argument, in the Principles of Human Knowledge (1710) and the Three Dialogues (1713), was that the primary qualities, no less than the secondary qualities, depend for their existence on being perceived. The chalk, considered in itself, is not white; it is not extended; it is not solid. It is a complex of ideas, and ideas require a mind. The famous formula: esse est percipi, “to be is to be perceived.”

This was a startling argument, and it has been much mocked. It was also a serious one. Berkeley’s reasoning was that the empiricist case against the secondary qualities turned on the fact that we have no experience of those qualities apart from the perception. Extend the argument to the primary qualities and the conclusion follows: we have no experience of the qualities apart from the perception. The “material substance” that Locke had posited as the bearer of the qualities is, then, an unnecessary hypothesis. God is the mind that perceives everything, all the time.

Berkeley’s philosophy had limited influence in Britain; it was too strange. It had more influence in Germany, where it fed into the development of Kant and the post-Kantian idealists. It has had a strange afterlife in twentieth-century philosophy, where Berkeley has been read as an anticipation of various anti-realist positions in the philosophy of perception. The honest judgment is that Berkeley was right about some technical points in the philosophy of perception and wrong about the implication that the natural world exists only when perceived. The latter view, whatever its philosophical merits, has not proved a useful basis for natural science.

David Hume and the radicalization

David Hume (1711–1776) was the formidable skeptic of the tradition, the figure who took the empiricist premises and refused to fudge the consequences. The Treatise of Human Nature (1739–1740) was the book that, in Hume’s own melancholy later judgment, “fell dead-born from the press.” The Enquiries (1748, 1751) were a more accessible restatement, and they were the books that made Hume’s reputation.

The central argument of the Enquiry Concerning Human Understanding is about causation, and it is one of the most influential philosophical arguments ever written. We believe, Hume said, that fire causes heat, that bread nourishes, that the sun will rise tomorrow. We believe these things because we have observed, repeatedly, that A is followed by B. The habit of mind is so strong that we cannot shake it off, even when we try. But the habit is not a rational insight. There is no logical contradiction in supposing that fire will, the next time, freeze rather than heat, or that the sun will fail to rise. We have no experience of the necessary connection between A and B; we have only the repeated observation of A’s being followed by B. The expectation is psychological, not logical.

The argument seems innocuous, but it is not. If Hume is right, then the rational foundations of natural science are more modest than scientists had supposed. We do not know that the sun will rise tomorrow; we are psychologically committed to believing that it will. The argument also seems to undermine the foundations of traditional metaphysics. If we have no rational insight into necessary connections, then we have no rational insight into the existence of God, the immortality of the soul, the reality of material substance, or the truth of the cosmological and teleological arguments.

Hume’s Dialogues Concerning Natural Religion (1779, published posthumously in 1779 against his express instructions) pushed the skeptical line further, applying it to the argument from design. Even if we grant that the universe has the marks of design, the best we can conclude is that the designer has a great deal of power and intelligence — not that the designer is omnipotent, omniscient, or morally good. The bad-design argument — that the world contains a great deal of obvious suffering and waste — is one of the Dialogues’s sharpest moves. The work is, incidentally, a small masterpiece of philosophical fiction. The character of Philo, the skeptic, is given the best lines; Cleanthes, the defender of the design argument, is given the second-best lines. This is not a coincidence.

The scholars are still arguing about what to make of Hume. Some read him as a thoroughgoing skeptic who could not bring himself to believe any of the conclusions of the Enquiries and Dialogues. Some read him as a mitigated skeptic who was, in the end, a kind of naturalist. Some read him as a precursor of the logical positivists of the twentieth century. The New Hume literature of the last forty years has produced books arguing each of these positions at length. The debate is not closed, and it is not going to be closed, because Hume is one of those philosophers whose writings genuinely permit more than one reading. He was that good.

The influence

The empiricist tradition is the philosophical backbone of modern natural science. The contemporary scientific method — observation, experiment, the careful analysis of evidence, the willingness to revise conclusions in the face of contrary data — is a direct descendant of the empiricist program. The connection is sometimes overstated — Newton was not a strict empiricist about the method of natural philosophy, and the Royal Society was less faithful to Bacon’s program than its members liked to claim. But the connection is real, and it is the reason why the empiricist tradition is taught in every introductory philosophy course in the English-speaking world.

The tradition is also the philosophical backbone of the British political tradition. Locke’s theory of natural rights was grounded in the empiricist account of the origin of knowledge. The rights were not innate ideas; they were derived from the observation of the actual conditions of human life, and they were based on the requirements of human self-preservation and well-being. The Scottish Enlightenment — Hume, Smith, Ferguson, Reid — extended the empiricist program into the study of morals, politics, and economics. The result was a tradition of social science that is, in many ways, the ancestor of contemporary behavioral economics, evolutionary psychology, and the sociology of norms. This is not the only tradition in modern social science, and it has been heavily criticized — by Marx, by the Frankfurt School, by the postcolonial critics. But it is one of the founding traditions, and the empirical habit of mind is one of its main legacies.

The critiques

The rationalist critique came from Descartes, Spinoza, and Leibniz, and it took the form of an appeal to the structure of reason itself. Certain principles — the principle of non-contradiction, the principle of sufficient reason, the principle of identity — cannot be derived from experience, since they are necessary for the very possibility of experience. The empiricists were trying to build a house without a foundation.

The Kantian critique came from Kant’s Critique of Pure Reason (1781) and it was, in some ways, the most serious of the three. Kant argued that the empiricist account of the origin of knowledge was based on a false dichotomy between sensation and reason. Knowledge is a product of both — the matter of sensation and the form of the categories of the understanding (causality, substance, unity, etc.). The empiricists had been right that the categories are not derived from experience; the rationalists had been right that there are necessary principles of reason. Both were wrong about the relationship between the two.

The Romantic critique came from Herder, the Schlegel brothers, Schleiermacher, and the broader German Romantic reaction. The complaint was that the empiricist account of knowledge was inadequate to the richness of human experience — that it missed feeling, imagination, history, language, and the cultural particularity of human life. The complaint was, in its strong form, exaggerated. The empiricists had not denied the existence of these dimensions of human life; they had attempted to give a different account of them. But the complaint was not empty, and it was one of the sources of the German tradition of Geisteswissenschaften — the human sciences — that has been so influential in twentieth-century European thought.

Why this tradition still matters

The contemporary debate in the philosophy of mind, the philosophy of perception, and the philosophy of science is, in a way that practitioners do not always acknowledge, a continuation of the debate that the British empiricists began. The contemporary defenders of the empiricist program in cognitive science — the connectionists, the Bayesian modelers, the embodied-cognition theorists — are doing, with better instruments, what Locke and Hume tried to do with very few instruments. The contemporary critics of the program — the phenomenologists, the Wittgensteinians, the heirs of Heidegger — are doing, with different instruments, what the rationalists and Romantics did. The basic questions — about the proper relationship between mind and world, the proper basis for knowledge, the proper method for the investigation of nature — are the same questions. The terms have changed. The questions have not.