Source of knowledge

The lever is a genetic argument: trace any idea back to its source and one finds only an impression of sensation or reflection, never a content given in advance. Locke opens the Essay by demolishing the universal-consent argument advanced for innate ideas (no principle is known to children or idiots), which leaves the mind as white paper to be furnished; Hume sharpens the criterion into a polemical weapon, demanding that one exhibit the impression a term derives from, failing which it is empty of meaning. This is the exact reversal of Descartes's rationalism, which made the innate idea the bedrock of knowledge.

Locke, Essay Concerning Human Understanding, book I (against innate ideas) and II, 1 · Hume, Enquiry Concerning Human Understanding, section II

The Epicurean Canonic, the theory of the criterion of truth, is a forthright empiricism: all knowledge derives from sensations, from preconceptions (prolēpsis), the general concepts sedimented by repeated experience, and from the feelings of pleasure and pain. The senses by themselves never err: error arises in the judgment that opinion adds. Reason only combines what experience supplies.

Epicurus, Letter to Herodotus, 37-38 · Diogenes Laertius, Lives, X, 31-34 (the Canonic)

All knowledge worthy of the name begins in the senses and observation: this is the empiricist foundation that Locke and Hume will make a school of. Yet Bacon does not trust the senses left to themselves, which he holds to be fallible and deceptive; he supplements them with provoked experience, the experimentum, and the methodical apparatus that corrects them. Experience is primary only on condition of being disciplined: neither pure rationalism nor naive empiricism, but reason in the service of regulated observation.

Novum Organum, I, §50 and §95 · The Advancement of Learning, II

Against Platonic innatism, knowledge starts from perception, from which induction draws out universal principles, a legacy the Scholastic tradition would later sum up as "nothing is in the intellect that was not first in the senses". The empiricism remains moderate, since the active intellect then grasps essences, hence a non-extreme position.

Posterior Analytics, II.19 · On the Soul, III.4-8

Nietzsche overturns the Platonic hierarchy: it is not reason that would reach the true against deceiving senses, it is the senses that do not lie, and reason that falsifies their testimony of becoming by substituting being, unity, the thing. The intelligible back-world, from Plato to Kant, is a fiction born of decadence. But Nietzsche does not lapse into naive empiricism: there is neither brute fact nor immaculate perception, all knowledge is interpretation from a perspective, governed by the needs of life and the will to power. An empiricism of the body and the senses, then, but radicalized into perspectivism.

Twilight of the Idols, Reason in Philosophy · Beyond Good and Evil, §§ 16-17

Thomas refuses innatism and holds, following Aristotle, that all knowledge begins with the senses, the intellect being at first like a blank slate on which nothing is written. But the empiricism is tempered: the agent intellect does not passively receive the sensible, it abstracts from it the intelligible form, drawing the universal out of the perceived particular. Knowledge therefore starts from experience without reducing to it, which keeps Thomas on the empirical side without making him a strict empiricist, the activity of the mind having its irreducible share.

Summa Theologiae, Ia, q. 84-85

Utilitarianism extends the British empiricism of Locke and Hume: all knowledge, moral as well as factual, derives from experience, from the observation of pleasures, pains and consequences. No innate ideas, no a priori truths: the mind starts from the sensible, and the calculation of observable effects replaces the rational deduction of principles.

Bentham, Introduction to the Principles of Morals and Legislation · Mill, A System of Logic

In the empiricist line of Locke and Hume, Bentham holds real only what can be observed and measured, and suspects any term that answers to no sensible entity. This drives his critique of fictions: an expression like natural right claims to name a thing while no fact corresponds to it, and is merely a word with which a demand is cloaked rather than justified. His method is thus resolutely inductive and naturalistic, anchored in the experience of pleasures and pains rather than in a priori rational principles, and it is on that ground that he dismisses natural rights.

Anarchical Fallacies (natural rights, nonsense upon stilts)

His knowledge, he says, is drawn from a long experience of modern things and a continual reading of ancient ones: it is from the observation of cases, diplomatic and historical, that the maxims emerge, not from a priori deduction. An empirical, inductive method applied to human affairs.

The Prince, Dedicatory Letter · Discourses on Livy, Book I, Preface

Since every rational deduction of the essence of things runs aground on the equipollence of doctrines, all that remains for conduct is what imposes itself without asking our leave: sensory appearances and phenomena. The skeptic does not erect them into a source of truth; he undergoes them as a purely practical criterion, enough to act on without asserting anything. Sextus' epithet, the Empiricist, marks this reversal: no longer deducing the real from above, by speculative reason, but relying on the given, from below, without claiming to pierce its nature.

Sextus Empiricus, Outlines of Pyrrhonism, I, 21-24 · Diogenes Laertius, Lives, IX, 105-106

Pragmatism is rooted in experience rather than pure reason: James develops a radical empiricism in which relations themselves are given within the flux of experience, and Dewey grounds all thought in the organism's transaction with its environment. Knowledge proceeds from experimentation and its observable consequences, in the lineage of British empiricism, which it extends while ridding it of the idea of an inert sense datum.

James, Essays in Radical Empiricism (1912) · Dewey, Experience and Nature (1925)

Heir to Antisthenes and his nominalism, Diogenes recognises only sensible individuals and holds Plato's general Ideas to be empty words: "I can see a table and a cup, ran this line of thought, but not tablehood or cuphood". The knowledge that counts is taken from experience and concrete practice, not from the contemplation of intelligible essences. It is a nominalist empiricism, more polemical than systematic.

Diogenes Laertius, Lives, VI, 53

Against the idealism that derives the real from ideas, Marx roots knowledge in material conditions and social activity: one starts from what human beings do and produce, not from what they imagine. Yet he also rejects the contemplative empiricism of the old materialism, which passively receives the sensory given: to know is a praxis, an active and transforming relation to the world. The source stays on the side of experience, but reworked through practice rather than through pure reason.

Theses on Feuerbach, I and V · The German Ideology, I

Montaigne distrusts abstract reasonings, which can prove a thing and its opposite, and prefers to them the teaching of experience: the last essay, "Of Experience", makes patient commerce with things and with oneself the only accessible wisdom. He builds no empiricist system, but his leaning is clear, to know is to have lived, observed and tested rather than to have deduced. Reason remains "a two-handled pot, that one can grasp by the left or the right", too pliant to ground knowledge on its own.

Essays, III, 13, "Of Experience" and II, 12

A physician of the Empiric school, nicknamed "the Empiric", Sextus takes as his sole guide in life what shows itself: the phenomena (phainomena), the affections, the repeated observation proper to the arts. But this empiricism carries no dogma: he does not assert that the senses deliver the real, only that they deliver what appears, the one ground on which the skeptic consents to move. Against the rationalism that claims to infer the hidden from signs, he refuses any passage from the apparent to the non-apparent. His leaning is thus empiricist, but held short of the extreme, for he founds no theory of knowledge at all.

Outlines of Pyrrhonism, I, 21-24 (the criterion of the phenomenon) · Against the Mathematicians, VIII (Against the Logicians)

Against Platonic innatism, Aristotelianism holds that all knowledge begins in sense perception: nothing is in the intellect that was not first in the senses. Induction rises from perceived particulars to universal principles, yielding a moderately empiricist position, the intellect remaining required to grasp essences.

Aristotle, Posterior Analytics, II, 19 · Aristotle, On the Soul, III, 4-8

Antisthenes, the cynics' forerunner, opposes Platonism with a radical nominalism: I can see a horse, but not horseness. Only sensible individuals exist, grasped by perception; general Ideas are empty words. The knowledge that counts is taken from experience and concrete practice, not from the contemplation of intelligible essences.

Diogenes Laertius, Lives, VI · Simplicius, Commentary on the Categories

Historical materialism derives knowledge from material conditions and social activity, not from first ideas: it is life that determines consciousness, not the reverse. Against passive empiricism as much as against idealism, knowledge is worked out in praxis, the practical, transforming relation of human beings to their world.

Marx and Engels, The German Ideology · Marx, Theses on Feuerbach

Odysseus's knowledge comes not from pure reasoning but from experience of the world: the proem praises him for having seen the cities of many men and known their minds. It is by roaming, undergoing, observing that he learns, each ordeal adding to his knowledge of men and things. His intelligence is that of one who has seen much, not of one who has deduced much.

Odyssey, I, 3 (the proem)

For the Stoics, the soul at birth is like a blank sheet: all knowledge begins with the impressions (phantasiai) that the senses inscribe on it, and common notions form by the accumulation of experiences. The criterion of truth is the cataleptic impression, the one that grasps its object with such self-evidence that it compels assent. An empiricism of the source, then, but governed by a reason that assents or suspends.

Diogenes Laertius, Lives, VII · Cicero, Academica, II

A phenomenologist, Beauvoir holds knowledge to be rooted in lived, embodied experience: the body is not one object among others but the situated standpoint from which the world takes on meaning. Her method, in The Second Sex, starts from concrete data, biology, history, testimony, rather than from a rational principle laid down a priori. This sets her on the side of experience, without making her a classical empiricist, since experience is always that of a freedom in situation.

The Second Sex, Introduction · The Ethics of Ambiguity

Liberating knowledge is established neither by scriptural authority nor by rational speculation, but by examination and direct experience: the Buddha invites one to test for oneself, come and see, and decisive knowledge arises from a perception refined by meditation. The source is therefore experiential, though this experience includes contemplative insight and not the five senses alone.

Kalama Sutta (Anguttara Nikaya) · Satipatthana Sutta (the foundations of mindfulness)

The knowledge that matters is not the discursive knowing that defines and argues, but an embodied skill acquired through repeated dealings with things: the butcher, the wheelwright, the swimmer could not explain their art, and yet they possess it to their fingertips. This primacy of practical experience and direct contact over abstract reasoning leans to the empirical side, but it is an empiricism of the gesture rather than of the senses, with no theory of perception as a source of true propositions.

Zhuangzi, ch. 3 (Cook Ding) · Zhuangzi, ch. 13 (Wheelwright Bian)

Buddhism makes personal examination and direct experience, not authority or tradition, the source of liberating knowledge. Decisive knowledge proceeds from a perception refined by meditation, more than from a priori intellection: one tests for oneself the root of suffering and its cessation, as one verifies a remedy by applying it.

Kalama Sutta (Anguttara Nikaya III.65) · Satipatthana Sutta

Confucian knowledge is won through study, observation and the imitation of the ancients, not through innate ideas. To learn is to steep oneself in the texts, the rites and the examples, a patient formation through experience and tradition rather than through rational deduction; the Master himself claims to be not one born wise, but a lover of antiquity, quick to seek it there.

Analects (Lunyu), VII.1 and VII.20 · Analects, II.15

The dominant epistemology of the philosophes is that of Locke: the mind is at first a blank slate, and all our ideas come from experience. Condillac draws from this a thoroughgoing sensationism in which even the operations of the mind reduce to transformed sensations. This empiricism feeds the critique of innate ideas, the supposed weapons of prejudice and authority. The current is not unanimous, however: a rationalist strand inherited from Descartes persists, and Kant will go beyond the alternative by showing that experience itself presupposes a priori forms of the understanding.

Locke, Essay Concerning Human Understanding, book II · Condillac, Treatise on the Sensations

Confucian knowledge is won by assiduous study of the Ancients, observation and practical experience, joined to reflection: learning without thought is vain, thought without learning is perilous. Knowledge is not pure speculation but wisdom to be applied, anchored in tradition and the scrutiny of the real, hence an empiricist leaning tempered by the demand for reflection.

Analects, II, 15 (learning without thought, thought without learning) · Analects, VII, 8 and II, 17 (active study; knowing what one knows and does not know)

Epictetus' whole discipline bears on impressions (phantasiai): they impose themselves on us from outside, sensory material we do not choose, but the sage's proper work is their use and the assent one grants or withholds. The source of the material is empirical; right knowledge depends on the correctness of the judgment that sorts it, which keeps Epictetus on the side of experience without abolishing the share of reason.

Discourses, I, 27 and II, 18 · Enchiridion, 1 and 5

Peirce is a scientist for whom all knowledge is tested against experience, and doubt itself arises only from a sensible jolt, never from a decision of the mind: the bent is clearly empiricist. But he refuses the atomist empiricism of pure sensation and restores to inference, logic and real generalities a constitutive role, abduction introducing ideas no observation contains. Neither blank slate nor innatism: an empiricism tempered by logic, nearer to criticism than to Hume.

Some Consequences of Four Incapacities (1868)

Taoism is wary of conceptual, bookish knowledge, which carves up and names while the Tao exceeds all speech: the Tao that can be named is not the eternal Tao. True knowledge is not rational accumulation but unlearning and intuitive accord with the course of things, a knowing of the concrete and the spontaneous, closer to lived experience than to discursive reason.

Laozi, Tao Te Ching, ch. 1 and 48 · Zhuangzi

Sartre's phenomenological ontology starts from the lived experience of consciousness, anguish, nausea, the look of the other, rather than from rational deductions or pure sensory facts. Consciousness is from the outset an intentional relation to the concrete world, and it is by describing it that one knows it. But the pre-reflective cogito remains a Cartesian-type foothold, which keeps Sartre near the median, leaning slightly toward described experience.

Being and Nothingness, Introduction · The Imaginary

Primacy goes to intuition: the concept only fixes and stores, in abstract coin, what perception alone first gives; discursive reason is sterile away from that source. But intuition is itself already shaped by the a priori structures inherited from Kant, hence a mixed position that leans toward empiricism without belonging to it.

The World as Will and Representation, Book I

The movement privileges concrete existence, lived in the first person, against the abstract rational systems that claim to deduce everything (Hegel): the truth that commits is grasped in the situation, in anguish, in choice, not in a disembodied reason. It is not for all that an empiricism of facts, and the figures diverge, which keeps the movement near the median, leaning slightly toward lived experience.

Kierkegaard, Concluding Unscientific Postscript · Sartre, Existentialism Is a Humanism

Husserl's position espouses neither empiricism, which reduces all knowledge to sensation, nor the rationalism that deduces the real from reason alone: this is its distinctiveness. His "principle of principles" is that every originarily giving intuition is a source of right for knowledge, but intuition is not only sensory. Alongside the perception of fact there is an intuition of essences, an immediate giving of the general with its own evidence. Knowledge is thus governed not by a privileged faculty but by the given itself, as it presents itself: a third, intuitionist term that passes between the two classic poles rather than arbitrating them.

Ideas I, §24 (the "principle of principles") · Logical Investigations, VI

Phenomenology refuses the empiricism / rationalism alternative: against the sensualism that reduces the mind to impressions, and against deductive rationalism, it returns to the intuition of what gives itself. The epoché brings out the essential structures of experience, grasped in an intuition of essences (Wesensschau) that is both a priori and grounded in lived experience. Hence a third-way position, close to criticism.

Husserl, Ideas Pertaining to a Pure Phenomenology, I · Husserl, Logical Investigations

On brahman, which is neither perceived nor inferred from the world, the only valid source is revelation (śruti), the word of the Upaniṣads: sense experience gives only the manifold, and reasoning alone cannot establish the absolute. But Śaṅkara is no fideist: reason (yukti) is indispensable to interpret Scripture, resolve its apparent contradictions and refute rival schools, and the teaching saves only when it becomes direct experience of the self. The primary material is thus not empirical but scriptural and rational, which places him on the side of reason without making him a pure rationalist, the authority of revealed testimony remaining first.

Commentary on the Brahma Sūtras, I.1.3-4 · Upadeśasāhasrī

True knowledge comes not from the senses, which reach only images of the sensible, but from the intellect turned toward the intelligible, which it contemplates from within: the soul recovers the Forms within itself because it proceeds from the Intellect. At the summit, the highest knowledge is no longer even discursive but an immediate grasp, indeed a union that surpasses thought. This inward, rational source of knowledge, against all empiricism, places Plotinus firmly on the side of rationalism.

Enneads, V, 3 (On the Knowing Hypostases) · Enneads, V, 5

Socrates seeks the true not in the observation of nature, from which he has turned away, but in the regulated examination of reasons: one starts from the interlocutor's opinions and follows the argument wherever it leads, to contradiction or to agreement. It is reason in dialogue, not sense experience, that yields the definition; yet there is nothing in him of the doctrine of innate ideas or recollection, which Plato will add.

Plato, Phaedo, 96a-99d (the turn away from natural science) · Cicero, Tusculan Disputations, V, 4, 10 (Socrates brought philosophy down from the heavens)