Epistemology

Imagine dropping a stone a thousand times, and a thousand times it falls. You are utterly certain it will fall on the thousand-and-first. But pause and ask: what, exactly, justifies that certainty? You have never seen the “necessity” of the stone’s falling — you have only seen stones falling. The leap from what has happened to what will happen seems obvious, yet when we examine it, no logical proof holds it up. This small abyss, opened by David Hume in the eighteenth century, has never quite been closed. It swallows causation, induction, the self, and much of metaphysics — and it is the best place to start understanding why Hume is perhaps the most unsettling of modern philosophers. ...

In 1963, Edmund L. Gettier (1927–2021) published in the journal Analysis a three-page article titled “Is Justified True Belief Knowledge?” (Analysis 23, 1963, pp. 121–123). In fewer than a thousand words, Gettier overturned a consensus of more than two millennia: the definition of knowledge as justified true belief. Rarely has so short a paper produced so lasting an impact in the history of philosophy. 1. The Classical Definition: JTB The tripartite definition of knowledge — knowledge as Justified True Belief (JTB) — is often traced to Plato’s dialogue Theaetetus (c. 369 BC), where Socrates successively examines and refutes three definitions of knowledge. In the passage known as the “account” definition (logon didonai, 201d–210a), something close to the JTB conception appears, though Plato ultimately rejects it as well. ...

What distinguishes a scientific theory from a myth, an ideology, or a metaphysical system? Why do we accept as knowledge what physics tells us, but not what astrology — or psychoanalysis, at least in its more speculative form — claims? These questions, simple at first glance, opened in the twentieth century one of the most consequential debates in contemporary philosophy. Its two central figures — Karl Popper and Thomas Kuhn — formulated answers that, far from reconciling, redrew the landscape of epistemology. ...

Probably no philosophical text, in twenty-five centuries of Western tradition, has been more commented, paraphrased, glossed, and reinterpreted than the passage that opens Book VII of Plato’s Republic. In three pages of translation, Socrates asks Glaucon to imagine men chained from birth at the bottom of a cave, seeing only shadows projected on a wall — and proposes that this scene describes, with startling fidelity, the common condition of human beings. This is the Allegory of the Cave, and it is at once one of the most famous pieces of philosophy and one of the most systematically misunderstood. To read it rigorously, it must be situated in its context: it is the third of three articulated images — following the metaphor of the sun and the divided line — that constitute the core of Plato’s mature thought. ...

Few questions run through the history of philosophy as persistently as this one: what is truth? From Parmenides to Foucault, every era has reformulated this inquiry according to its own assumptions about reason, language, being, and power. This article traces the major stations of that journey — from Greek alétheia to the contemporary crisis of post-truth — not as a mere chronology, but as a map of the tensions that still define philosophical thought. ...

Few distinctions have shaped the history of philosophy as profoundly as that between what we can know independently of experience and what we can know only through it. The distinction between a priori and a posteriori spans centuries of epistemological debate — from medieval logicians to Leibniz, from Hume to Kant, from nineteenth-century empiricist critiques to the upheavals of contemporary analytic philosophy. To understand it is to understand the very problem of knowledge. ...

There are few moments in the history of philosophy that can rival, in sheer radicality and consequence, the one in which René Descartes, secluded in his Dutch stove-heated room, discovered that the very act of doubting contains within itself an unshakeable certainty: whoever doubts, thinks — and whoever thinks, exists. The cogito — formulated in slightly different ways across three major works — became not merely the starting point of Cartesian philosophy but the founding act of all modern philosophy. Through it, human subjectivity installed itself at the centre of philosophical inquiry and has remained there, in various guises, for four centuries. ...

Few distinctions have been as decisive for the history of Western philosophy as the one that separates doxa (δόξα, opinion) from episteme (ἐπιστήμη, knowledge). Since the Pre-Socratics, the effort to move beyond the plane of appearances toward well-grounded understanding has constituted the central impulse of philosophical inquiry. Doxa designates the unjustified judgment, the belief that rests on sensory appearances or social convention; episteme, by contrast, aspires to justified truth — to knowledge sustained by necessary reasons. ...

Few philosophical gestures are as radical — and as productive — as the deliberate decision to withhold judgment. Epoché (ἐποχή), the suspension of assent, runs through the history of Western philosophy like a thread connecting ancient skepticism to contemporary phenomenology, passing through Cartesian doubt and British empiricism along the way. Born as a practice of life among the Pyrrhonian skeptics, who sought in it the tranquility of the soul, epoché was reclaimed twenty-three centuries later by Edmund Husserl as the founding method of phenomenology — the path to “the things themselves.” ...

This is the fifth and final article on Joseph Maréchal’s Le point de départ de la métaphysique (The Starting Point of Metaphysics). We have traced the full arc of Maréchal’s historical project: from the ancient Greek tradition and Scholasticism (Cahier I), through the rationalist-empiricist conflict (Cahier II), into the depths of Kant’s critical philosophy (Cahier III), and through the analysis of post-Kantian idealism from Fichte through Schelling to Hegel (Cahier IV). In this fifth article, we arrive at Cahier V — Le thomisme devant la philosophie critique — the heart of the work, published in 1926 — where Maréchal undertakes a systematic comparison of Thomism with critical philosophy and presents his own original philosophical argument: that intellectual dynamism toward Absolute Being is a transcendental condition of the very possibility of knowledge, and that a genuine metaphysics of being is therefore not merely defensible but philosophically necessary. ...

This is the fourth of five articles on Joseph Maréchal’s Le point de départ de la métaphysique. In the preceding articles, we traced the classical tradition of knowledge from Aristotle to Thomas Aquinas (Cahier I), the conflict between Rationalism and Empiricism culminating in Hume’s scepticism (Cahier II), and the detailed analysis of Kant’s critical philosophy — the Transcendental Aesthetic, Analytic, and Dialectic (Cahier III). Now, in Cahier IV — entitled Le système idéaliste chez Kant et les postkantiens and published posthumously in 1947, three years after Maréchal’s death — we examine how post-Kantian idealism developed the transcendental turn inaugurated by Kant, carrying it to consequences that Kant himself had neither foreseen nor authorized. ...

This is the third of five articles on Joseph Maréchal’s Le point de départ de la métaphysique. In the first two articles, we followed Maréchal’s historical survey from the ancient Greek tradition through medieval Scholasticism (Cahier I) and then through the modern conflict between rationalism and empiricism (Cahier II). That survey ended with Hume’s devastating skepticism — the revelation that neither the rationalist appeal to innate ideas nor the empiricist appeal to sense experience could ground the objective necessity that genuine knowledge requires. In this third article, we turn to Cahier III, which Maréchal devotes entirely to Immanuel Kant’s Critique of Pure Reason — the most ambitious attempt in modern philosophy to answer Hume’s challenge, and the text that casts the longest shadow over Maréchal’s entire project. ...

This is the second of five articles on Joseph Maréchal’s Le point de départ de la métaphysique (The Starting Point of Metaphysics). In the first article, we followed Maréchal’s reading of the classical tradition from the pre-Socratics through Thomas Aquinas, showing how ancient and medieval thought largely assumed a direct cognitive contact with being without needing to systematically justify that assumption. In this second article, we turn to Cahier II, in which Maréchal examines the great modern debate between rationalism and empiricism — and shows how both traditions, despite opposing each other on almost every point, ultimately leave the problem of objectivity unresolved and prepare the ground for Kant’s revolutionary critique. ...

This is the first of five articles dedicated to Joseph Maréchal’s monumental work Le point de départ de la métaphysique (The Starting Point of Metaphysics), published in five notebooks (cahiers) between 1922 and 1947. Each article follows one cahier, tracing Maréchal’s ambitious project: to demonstrate, through a rigorous historical and critical method, that a genuine metaphysics of being is not only possible after Kant but is in fact demanded by the very structure of human knowledge. This first article covers Cahier I, which examines the classical tradition from ancient Greece through the end of medieval Scholasticism. ...

Bertrand Russell Born in 1872 into an influential British aristocratic family — he was the grandson of a prime minister — Bertrand Russell had one of the longest and most varied careers in philosophy: he was a logician, mathematician, essayist, educator, and political activist, spanning nearly a century of history. He studied at Cambridge, received the Nobel Prize in Literature in 1950, and, faithful to his pacifism, was imprisoned during the First World War and led, in his nineties, the campaign against nuclear weapons (the Russell-Einstein Manifesto, 1955). He is, with Frege and Wittgenstein, one of the founders of analytic philosophy. ...

Donald Davidson was one of the most original analytic philosophers of the second half of the twentieth century. A professor at the University of California, Berkeley from 1981, following positions at Stanford, Princeton, and Rockefeller, Davidson constructed a philosophical system remarkable for its internal coherence: his philosophy of mind, theory of action, semantics, and epistemology are closely interconnected, articulated around the themes of events, causation, truth, and interpretation. Key Concepts Anomalous Monism (Mental Events, published in Experience and Theory, 1970): Davidson argues that mental events are identical to physical events, but that this identity does not entail the existence of strict psychophysical laws. The central argument distinguishes three theses: (1) there is causal interaction between mental and physical events; (2) causally related events are covered by deterministic laws; (3) there are no strict laws connecting mental and physical descriptions. Davidson’s solution is to hold that a single event can be described in both mental and physical terms — but that mental properties are anomalous: there are no psychophysical laws enabling reduction of the mental to the physical. This is a form of monism (physics is the only causal domain) combined with anomaly (the mental is not reducible to physical laws). ...

G.E. Moore British philosopher, co-founder — alongside Russell and Frege — of analytic philosophy. His critique of British idealism and his work in ethics decisively influenced the entire analytic tradition of the 20th century. Key Concepts Naturalistic fallacy: the error of defining the good in terms of natural properties (pleasure, evolution, desire). The good is simple, indefinable, and non-natural — it cannot be reduced to any empirical property. A central critique of utilitarianism and ethical naturalism Open question argument: for any natural property X, it always makes sense to ask “Is X good?” — if the good were identical to X, the question would be absurd. This proves that good ≠ X Moral intuitionism: fundamental moral values are known by direct intuition, not by inference or definition. Ethics is an autonomous science, not reducible to natural sciences Common sense realism: against the idealism of Berkeley and Hegel — the external world exists independently of the mind. Defense of common sense realism as the philosophical starting point Proof of the external world: “here is a hand, here is another” — he argues that we can prove the existence of the external world with more certainty than any abstract philosophical premise that denies it Conceptual analysis: the central task of philosophy is analysis — decomposing complex concepts into their simpler, more precise components; the program that defines analytic philosophy Intrinsic goods: certain states are good in themselves (friendship, beauty, knowledge) — independently of any consequence. A critique of hedonistic utilitarianism Influenced by Kant — deontological ethics and moral autonomy Russell — analytic program (mutual influence) Sidgwick — British moral intuitionism Influenced Russell and Wittgenstein — analytic philosophy Bloomsbury Group (Virginia Woolf, Keynes) — ethics and aesthetics Contemporary metaethics (intuitionism, moral realism) Karl Popper — theory of knowledge Works Principia Ethica (1903); Ethics (1912); Philosophical Studies (1922); Some Main Problems of Philosophy (1953). ...

Hilary Putnam Hilary Whitehall Putnam was one of the most versatile and intellectually honest philosophers of the twentieth century. Over a career spanning six decades, mostly at Harvard, Putnam pursued an unusual philosophical itinerary: he defended positions that he later criticised with the same energy with which he had established them. He was a functionalist and then rejected functionalism; a scientific realist and then proposed “internal realism”; a sympathiser with logical positivism and then its critic. This willingness for self-criticism is one of the hallmarks of his philosophical style. ...

Immanuel Kant Born in Königsberg, in East Prussia, in 1724, and never having strayed from his native city, Immanuel Kant led the methodical life of a university professor — so regular, tradition holds, that his neighbors set their clocks by his daily walk. It was, in his own words, the reading of Hume that “awakened him from his dogmatic slumber” and led him into a long decade of silence, at the end of which, already 57 years old, he published the monumental Critique of Pure Reason (1781). His work both closes and refounds Modernity, mediating the dispute between the rationalism of Descartes and the empiricism of Hume. ...

Imre Lakatos Imre Lakatos was a Hungarian-British philosopher of science and mathematics, a professor at the London School of Economics and one of the central figures in the debate on scientific rationality during the 1960s and 1970s. His work seeks an intermediate position between Popper’s falsificationism and Kuhn’s historical account: against the idea that a single refutation overturns a theory, but also against the idea that scientific change is mere irrational “conversion”. Lakatos proposed that the unit of scientific appraisal is not the isolated theory but the research programme, judged over time by its capacity to anticipate novel facts. He was also an original philosopher of mathematics, showing in Proofs and Refutations that mathematical knowledge grows through a dynamic process of conjectures, proofs, and counterexamples rather than by pure, finished deduction. ...