Philosophy

empiricism

The position that knowledge comes chiefly from sensory experience rather than from reason working on its own — the long counterweight to rationalism in Western thought.

A physician at a sickbed reasons one of two ways. He can ask what hidden process inside the body produces the fever, deduce its nature from a theory of humors or pneuma, and treat the cause his theory names. Or he can set the theory aside and ask only what has been seen: in which patients, after which signs, did which remedy precede recovery — and reach for the remedy that observation has paired with the cure, without claiming to know why it works. The second physician belonged, in the Hellenistic world, to a named school. Its members called themselves the Empirics, from empeiria, experience, and they made the quarrel between the two methods a doctrine before it was ever a chapter in the theory of knowledge.

Empiricism is the position that knowledge comes chiefly, and for the strongest versions entirely, from sensory experience rather than from reason operating on its own. It is less a single doctrine than a recurring stance, defined as much by what it denies as by what it asserts: there are no substantive truths about the world that the mind can reach by pure thought, prior to and independent of what the senses supply. Its standing opponent is rationalism, which holds that at least some real knowledge of the world is innate, or is arrived at by reason alone, without any contribution from the senses that could not in principle be dispensed with. The dispute is not over whether the senses matter — almost no one denies that — but over whether they are the sole well from which knowledge is drawn, and whether there is any faculty that can deliver truth about how things stand without first passing through them.

The ancient root

The stance is old, and its first articulations are double — one medical, one philosophical. Aristotle set the philosophical terms. Against his teacher’s school, which located the deepest realities in a realm the senses cannot touch, he held that the mind at the start is like a writing-tablet on which nothing is yet written, and that it acquires its contents through perception. There is nothing in the intellect, on this view, that did not arrive by way of the senses and the memory and experience built up from them; the universal is not recollected from a prior vision but abstracted, late, from many particulars first taken in by the eye and ear. This is not yet full empiricism — Aristotle keeps an active intellect and a robust confidence in demonstrative science — but it is the seed of the later formula, and it was Aristotle, not the empiricists who claimed him, who first made experience the ground floor of knowing.

The medical root ran in parallel and gave the stance its name. From the third century BCE a school of Greek physicians, beginning with Philinus of Cos and Serapion of Alexandria and counting Heraclides of Tarentum among its sharpest minds, defined medicine against the Dogmatists who reasoned from hidden causes. The Empirics held that the physician should rest on three things: his own observed cases (autopsia), the recorded cases of others (historia), and reasoning from the similar to the similar in the face of a new disease (hē tou homoiou metabasis). The unseen interior of the body, and the unseen causes the Dogmatists invoked, were declared either unknowable or simply beside the point: what cured was paired with what was seen, and that pairing, not a theory, was the knowledge. Galen, himself no Empiric, preserved the school’s outline in his treatises on the medical sects, and it is from him that its shape is best recovered.

The two roots meet in a single ancient figure. The only systematic Pyrrhonist whose works survive entire — Sextus Empiricus, active in the late second or early third century CE — was himself a physician of the empiric medical school, and his very surname records the affiliation. The skeptical machinery he transmits, the suspension of judgment over every claim that reaches beyond the appearances, is the medical Empiric’s distrust of hidden causes raised to a universal method. Sextus is careful to distinguish the two allegiances and does not simply equate them, but the temperament is the same: stay with what shows itself, withhold assent from what is merely inferred. The surviving Greek text of his Outlines of Pyrrhonism and his Against the Learned — edited in the modern critical form by Hermann Mutschmann in the Teubner volumes of 1912 and 1914 — is the channel through which this ancient suspicion reached the early modern world, and through which it entered the bloodstream of the philosophy that would later take the Empirics’ name. The wider architecture of that skepticism, the modes of suspension and the Academic counterpart, runs through the Latin witness Cicero and the surviving corpus of Sextus; what matters here is the narrower point of contact: the demand that knowledge keep to what experience delivers.

The scholastic formula

Through late antiquity and the Middle Ages the Aristotelian principle hardened into a slogan that the schoolmen handled with care: nihil in intellectu quod non prius in sensu — nothing in the intellect that was not first in the senses. Carried in the commentary tradition and sharpened in the universities, it became, within scholasticism, the standing axiom of the peripatetic theory of cognition. Thomas Aquinas built it into a full account: the human intellect has no innate ideas and no direct intuition of immaterial forms in this life, but works upon phantasms, the images supplied by the senses, abstracting from them the intelligible content it then knows. Yet the schoolmen also marked the formula’s limit. The mind contributes the act of abstraction; the agent intellect is no passive tablet but a light by which the intelligible is drawn out of the sensible. So the medieval version is a guarded empiricism of content wedded to a rationalism of operation: every idea enters through the senses, but the power that turns sensation into understanding is the intellect’s own. Later rationalists would seize on the gap; Leibniz, restating the slogan, would add the famous rider — nothing in the intellect that was not first in the senses, except the intellect itself.

The British program

Empiricism as a named and worked-out program belongs above all to a sequence of thinkers in the British Isles in the seventeenth and eighteenth centuries, conventionally grouped — by a later textbook convenience they did not themselves use — as Locke, Berkeley, and Hume. Francis Bacon had already turned the temper toward nature, insisting that the understanding be drained of its idols and led, by orderly observation and the patient gathering of instances, up from particulars rather than down from maxims. The named program proper opens with John Locke. In the Essay concerning Human Understanding of 1689 he set out to take an inventory of the mind, and began by emptying it: there are no innate principles, no truths stamped on the soul before experience. The mind at birth is white paper, void of all characters, and every idea it will ever hold can be traced to one of two springs — sensation, the input of the outer senses, and reflection, the mind’s perception of its own operations. Even the loftiest abstractions, on Locke’s account, are compounded, abstracted, or combined out of simple ideas that entered by these two doors and by no other.

Berkeley pressed the principle until it turned, in his hands, against the very material world it seemed to vouch for. If all the content of the mind comes from perception, then the supposed matter standing behind our perceptions — the inert substance we never perceive but only infer — is an idle posit, a something-we-know-not-what doing no work. He drew the radical conclusion that for sensible things to exist is to be perceived: the tree, the table, the warmth are bundles of perceived qualities and nothing besides, held in being by their being perceived. Far from a denial of the senses, this was the empiricist principle taken at its word — admit only what experience presents, and matter is not among the things experience presents.

Hume pressed it furthest, and with the steadiest nerve. Every idea, he held, is a faint copy of a prior impression; trace any idea to its impression and the content is there; fail to find the impression and the mind stands caught trafficking in an empty word. Turned on the most ordinary furniture of thought, the method bit hard. We see one event follow another, again and again, but we never perceive the necessary tie that would make the first produce the second; causation, examined, dissolves into constant conjunction plus a habit of expectation in the observer — a real question about the necessity we take to bind cause to effect, here denied any basis in what the senses deliver. The continuing self, sought among the impressions, is nowhere to be found: introspection turns up only a flux of perceptions, never the I that supposedly has them. Induction itself — the inference from observed cases to unobserved — rests on the assumption that the future will resemble the past, and that assumption, Hume showed, can be justified neither by reason nor by experience without arguing in a circle. The empiricist who follows the method to the end arrives not at a sturdy science but at a disquieting candor about how little observation, strictly construed, can underwrite.

The method, the sciences, and verification

What unites these thinkers is a method rather than a creed: claims about the world are to be tested against, and built up from, what observation actually delivers, and concepts that cannot be cashed out in experience fall under suspicion. The demand reshaped more than philosophy. It is one of the intellectual sources of the experimental natural sciences — the insistence that hypotheses answer to controlled observation, that authority and elegant deduction yield to the verdict of the instrument and the repeated trial. The laboratory is, in one light, the Hellenistic Empiric’s autopsia and historia given apparatus and a logbook.

In the twentieth century a stricter version became, briefly, a program with a weapon. The logical positivists held that a statement has factual meaning only if experience could in principle confirm or refute it, and turned this verification criterion against metaphysics, theology, and much traditional philosophy as so many strings of grammatical but cognitively empty words. The criterion proved famously hard to state. Pressed for the experience that would confirm or refute the verification criterion itself, its defenders found that the principle, by its own measure, said nothing — neither an empirical report nor a definition, and so, on its own terms, meaningless. The recoil was instructive: the demand to cash every concept out in experience, turned on its own formulation, came up empty-handed, and the fate of that program is studied under positivism. The discipline survived its strictest charter; the charter did not.

The wager against the suprasensory

Empiricism sits at a deliberate distance from the traditions much of the surrounding material concerns. Where a mystic or a Platonist locates the deepest knowledge beyond the senses — in a turning of the soul, an inner illumination, a direct acquaintance unavailable to ordinary perception — the empiricist takes exactly that move to be where error enters. Platonism and the Neoplatonism that radicalized it stake everything on a higher faculty: the nous that beholds the intelligible forms, the eye of the soul that sees what no bodily eye can, the ascent that culminates in a contact with the One past all sensation and discourse. The knowing prized by mysticism and by gnosis is precisely a knowing that bypasses the senses — and that the empiricist must count, at best, as a vivid experience about whose object nothing has been established, and at worst as the mind mistaking its own motions for a report from beyond. Even reason in the rationalist’s grand sense — a faculty that grasps necessary truths about reality by its own light — is, to the empiricist, reason overstepping: legitimate when it orders and infers from what the senses bring, suspect the moment it claims to deliver substantive news about the world on its own authority. (The Stoics had drawn their own hard line here, founding knowledge on the katalēptic impression, the sense-presentation so clear it could not be doubted; their Stoicism supplied much of the Hellenistic backdrop against which both the Empirics and the skeptics defined themselves.) The two camps make incompatible wagers about where the real comes through to the mind — through the gate of the senses, or through a faculty the senses never reach.

Scholarship and texts

The standard map of the dispute, treating both wagers in their strongest forms, is Peter Markie and Marina Folescu’s Rationalism vs. Empiricism in the Stanford Encyclopedia of Philosophy, which separates the rationalist’s several theses — the Intuition/Deduction thesis, the Innate Knowledge thesis, the Innate Concept thesis — so that empiricism can be defined precisely as their denial across a given subject area. For the ancient medical school and its bearing on Sextus, the SEP entry on Sextus Empiricus and its companion on the Empiric physicians set out the relation of the medical sect to Pyrrhonism. The primary ancient witness to the school’s founders and their dispute with the Dogmatists is preserved in Diogenes Laertius, Lives of Eminent Philosophers IX, in the connected account of Pyrrho and his successors, alongside Galen’s treatises On the Sects for Beginners and An Outline of Empiricism. For the British program, Locke’s Essay concerning Human Understanding (1689), Berkeley’s Treatise concerning the Principles of Human Knowledge (1710), and Hume’s Treatise of Human Nature (1739–40) and Enquiry concerning Human Understanding (1748) are the founding texts; the modern critical and historical literature runs through Jonathan Bennett’s Learning from Six Philosophers and the volumes of the Cambridge Companions to each figure.

The discipline at the heart of empiricism is a discipline of accounting: present the idea, and name the experience it is drawn from, or set the idea aside. It is a method built to find the empty word and refuse it — and its sternest application has always been the one turned inward, on its own warrants. Causation, the self, induction, finally the verification rule itself: each was brought to the counter and asked to show the impression it was minted from, and each, in the hands of empiricism’s most exacting practitioners, came up short of the coin it had promised. That a method should be most ruthless precisely where it examines its own credit is not a flaw the tradition stumbled into but the discipline doing what it was built to do; the candor about its limits is the empiricist’s signature, the price and the proof of taking experience as the only ledger that counts.