On Certainty

Overview

On Certainty is Wittgenstein's last philosophical work, written in the final months of his life in 1951 and published posthumously in 1969. It is a sequence of remarks — numbered, aphoristic, and without a continuous argument — in which he returns, one final time, to the questions of knowledge, doubt, and certainty that had preoccupied him throughout his career. The immediate provocation was the work of G. E. Moore, whose "proof of an external world" claimed to refute skepticism by holding up his hands and asserting "Here is one hand." Wittgenstein found Moore's proof unsatisfying, but he also thought the skeptic's demand for proof was misplaced, and On Certainty works out an account of knowledge and doubt that rejects both.

The book is now regarded as one of the most important contributions to epistemology in the twentieth century, and the source of one of Wittgenstein's most fertile late ideas: the notion of hinge propositions, the certainties that stand fast for us and that make judging and doubting possible at all. In these late remarks Wittgenstein recasts certainty not as a kind of especially well-grounded belief but as the bedrock on which the practice of judging rests — the inherited background against which all inquiry takes place.

Core Ideas

Hinge Propositions

The book's central idea is that of the hinge proposition. Wittgenstein observes that within our practices of inquiry and doubt there are certain propositions that stand fast for us — that I have two hands, that the earth has existed for a long time, that my name is what I think it is. These propositions are not held because we have verified them; they are not conclusions of inquiry but its presuppositions. They function like the hinges on which the door of inquiry turns: the hinges themselves do not move in the same way the door does, but without them the door cannot move at all. Hinge propositions are certain, but their certainty is not the result of evidence; it is the condition under which evidence-gathering and doubt are possible.

The Asymmetry of Doubt and Certainty

A recurring theme is the asymmetry between doubt and certainty. We can doubt this or that within a practice, but we cannot doubt everything at once, because doubting presupposes a background of taken-for-granted certainties. To doubt whether this is really a hand, I must rely on countless things I do not doubt — that I am awake, that I remember how to use the word "hand," that my eyes function. Radical skepticism, which claims to doubt everything, is therefore not a coherent global stance but a misuse of the language of doubt detached from the practices that give it sense. Doubt, for Wittgenstein, always occurs against a frame of reference that is not itself in doubt, and this frame is not arbitrary but grounded in our form of life.

The Critique of Moore

Wittgenstein's engagement with Moore is double-edged. He agrees with Moore that certain common-sense propositions — "Here is a hand" — are beyond reasonable doubt, and that the skeptic is wrong to demand their proof. But he denies that Moore has proved them. Moore's mistake, on Wittgenstein's view, is to treat the hinge propositions as if they were ordinary empirical claims that could be established by evidence, when in fact they function differently: they are the framework within which evidence operates. To say "I know I have a hand" is not to report a well-grounded finding but to mark a certainty that belongs to the bedrock of the language-game. The point is not that Moore is wrong about the conclusion but that he mislocates the kind of certainty involved.

Certainty as Grammar and Form of Life

In the late remarks, certainty increasingly shades into what Wittgenstein calls "grammar" and "form of life." The hinges of our inquiries are not discovered truths about the world so much as rules of the language-game — the commitments without which the game could not be played. That I have two hands is, in ordinary contexts, not something I know by checking; it is part of the background against which checking makes sense. This does not make hinge propositions arbitrary or immune to revision in principle, but it does mean that their certainty is practical and grammatical rather than evidential. Certainty, in On Certainty, is ultimately grounded in action — in the way we go on, the practices we inherit, and the form of life we share.

Historical Context

Wittgenstein wrote On Certainty between October 1950 and April 1951, in the last months of his life, as he was dying of cancer. The remarks were prompted by his reading of Moore's papers "A Defence of Common Sense" and "Proof of an External World," and they carry forward the concerns of his later philosophy — the emphasis on practice, language-games, and forms of life — into the domain of epistemology. The notebooks were edited for publication by G. E. M. Anscombe and G. H. von Wright and appeared in 1969, nearly two decades after his death. Their appearance came at a moment when epistemology was being reshaped by the post-Gettier debates, and the book offered a strikingly different perspective: instead of refining the definition of justified true belief, Wittgenstein questioned the assumptions about knowledge and doubt on which the whole enterprise rested.

Legacy

On Certainty has become one of the most discussed texts in twentieth-century epistemology and the principal source of the idea of hinge propositions, which has generated a substantial literature of its own. The book offers a distinctive response to skepticism that neither concedes the skeptic's demand for proof nor claims to have refuted it by argument; instead, it aims to dissolve the demand by showing that doubt always presupposes a bedrock of certainty. Its influence extends beyond epistemology into the philosophy of language, the philosophy of action, and the study of Wittgenstein's later thought. For philosophers working on knowledge, belief, and doubt, On Certainty remains an indispensable and endlessly suggestive text — one that resists systematization even as it transforms the way its readers think about what it is to be certain of anything.

Reception and Criticism

On Certainty was published in 1969, eighteen years after Wittgenstein's death, and its appearance transformed the landscape of epistemology. The book arrived at a moment when the post-Gettier debates were reshaping the theory of knowledge, and it offered a perspective that was radically different from the project of refining the definition of justified true belief. Instead of asking what fourth condition must be added to knowledge, Wittgenstein questioned the assumptions about knowledge and doubt on which the whole enterprise rested. This made the book simultaneously alien to the mainstream of analytic epistemology and deeply suggestive to philosophers looking for an alternative to the definitional approach.

The concept of hinge propositions has generated a substantial and ongoing literature. Some philosophers, including Danièle Moyal-Sharrock and Duncan Pritchard, have developed Wittgenstein's remarks into a systematic "hinge epistemology" that treats hinge certainty as a distinct epistemic category — neither knowledge nor belief but a kind of animal certainty that underlies both. On this reading, the hinges are the framework within which epistemic practices operate, and their certainty is not evidential but grammatical: it belongs to the rules of the language-game rather than to the claims made within it. This interpretation has been influential, but it has also been contested. Other readers, including Avrum Stroll and Michael Williams, have offered different accounts of what the hinges are and how they function, and the question of whether hinge certainty is epistemic, practical, or grammatical remains a live debate.

The book's response to skepticism has been particularly influential. Wittgenstein neither concedes the skeptic's demand for proof nor claims to have refuted skepticism by argument; instead, he aims to dissolve the demand by showing that doubt always presupposes a bedrock of certainty. This therapeutic approach — treating the skeptic's global doubt as a misuse of the language of doubt rather than as a false thesis to be refuted — has resonated with philosophers who find both Moorean common sense and traditional epistemological argument unsatisfying. The idea that certainty is grounded in action and form of life, rather than in evidence or argument, has also connected On Certainty to broader movements in the philosophy of language and the philosophy of action, and to the ongoing reinterpretation of Wittgenstein's later philosophy.

Critics have pressed on several points. Some argue that the notion of a hinge proposition is too flexible — that Wittgenstein never clearly specifies which propositions count as hinges or how the set of hinges changes over time — and that this makes the concept difficult to use as a tool of epistemological analysis. Others question whether the therapeutic dissolution of skepticism is really adequate to the skeptic's challenge, or whether it merely changes the subject. These criticisms have not diminished the book's standing; if anything, they have deepened the engagement with its ideas. On Certainty remains one of the most discussed texts in twentieth-century epistemology, and its influence continues to grow as philosophers find in its aphoristic remarks new resources for thinking about knowledge, doubt, and the bedrock of inquiry.

Further Reading and Connections

On Certainty was published posthumously in 1969, edited by G. E. M. Anscombe and G. H. von Wright, and it is available in several editions and translations. The text consists of numbered remarks, written between October 1950 and April 1951, and it is best read in short sections rather than straight through, since the remarks are aphoristic and non-linear rather than a continuous argument.

For the philosophical context, the Stanford Encyclopedia of Philosophy entry on "Ludwig Wittgenstein" situates On Certainty within the later philosophy and the hinge-proposition idea, and it is the best starting point for readers who want to understand the book's place in Wittgenstein's thought. The Internet Encyclopedia of Philosophy entry on "On Certainty" provides an accessible exposition of the hinge propositions, the critique of Moore, and the response to skepticism, and it is a good introduction for readers new to the text.

The literature on On Certainty has grown substantially since the 1990s. Danièle Moyal-Sharrock's Understanding Wittgenstein's On Certainty (2004) develops a systematic "hinge epistemology" that treats hinge certainty as a distinct epistemic category. Duncan Pritchard's work on epistemological disjunctivism draws on Wittgenstein's insights to develop a novel response to skepticism. Avrum Stroll's Wittgenstein (2002) and Michael Williams's Unnatural Doubts (1991) offer different interpretations of what the hinges are and how they function. The question of whether hinge certainty is epistemic, practical, or grammatical remains a live debate.

The book's engagement with G. E. Moore's "proof of an external world" is essential background. Moore's papers "A Defence of Common Sense" (1925) and "Proof of an External World" (1939) are the immediate provocation for Wittgenstein's remarks, and reading them alongside On Certainty gives a vivid sense of the philosophical conversation that produced the book. Wittgenstein agrees with Moore that certain common-sense propositions are beyond reasonable doubt, but he denies that Moore has proved them, and the distinction between agreement and proof is one of the book's most fertile insights.

The book connects to several other entries in this knowledge base. The hinge-proposition idea is a central topic in the epistemology and skepticism entries, and the concept of certainty is developed in the certainty wisdom entry. The book's late-Wittgensteinian approach to knowledge and doubt is discussed in relation to Roderick Chisholm's foundationalism and Edmund Gettier's challenge to the definition of knowledge. The concepts of knowledge, belief, and doubt provide the broader epistemological context, and Bertrand Russell's The Problems of Philosophy sets up the framework that Wittgenstein's late remarks transform.

For readers who want to explore the therapeutic dimension of Wittgenstein's later philosophy, On Certainty is the most important text. The book's approach to skepticism — dissolving the demand for proof rather than meeting it with argument — exemplifies the therapeutic conception of philosophy that Wittgenstein developed in the Philosophical Investigations and that he extends, in these late remarks, to the domain of epistemology. The idea that philosophical problems arise when language "goes on holiday" — when the concepts and practices that give our words meaning are detached from the contexts in which they function — is applied here to the concepts of knowledge, doubt, and certainty, and the result is a diagnosis of skepticism as a misuse of the language of doubt rather than a false thesis to be refuted.

The book's literary form — a sequence of numbered, aphoristic remarks — is itself philosophically significant. Wittgenstein did not write On Certainty as a treatise with a continuous argument but as a series of observations, questions, and provisional conclusions, and the form reflects his conviction that philosophy should not systematize but clarify. This makes the book difficult to summarize but rewarding to read slowly, as each remark builds on and qualifies what came before. The form has also influenced the style of later Wittgensteinian philosophy, which tends to be therapeutic, diagnostic, and attentive to the actual use of language rather than systematic and abstract.

The book's form — a sequence of numbered remarks rather than a continuous argument — has important philosophical implications. Wittgenstein did not write On Certainty as a treatise with a thesis to defend but as a series of observations, questions, and provisional conclusions, and the form reflects his conviction that philosophy should not systematize but clarify. The remarks are connected by themes rather than by logical deduction, and they circle around the same problems from different angles, gradually building up a picture of how knowledge, doubt, and certainty function in our lives. This makes the book difficult to summarize but rewarding to read slowly, as each remark sheds new light on what came before.

The numbering of the remarks — Wittgenstein used a continuous numbering system from 1 to 676 — has become a standard citation format, and references to On Certainty in the philosophical literature typically cite the remark number rather than the page. This reflects the aphoristic, self-contained quality of each remark: many can be read on their own as miniature essays on knowledge, doubt, or certainty, even as they gain depth from their place in the larger sequence. The form has influenced the style of later Wittgensteinian philosophy, which tends to be therapeutic, diagnostic, and attentive to the actual use of language rather than systematic and abstract.

For readers new to Wittgenstein, On Certainty is often recommended as the most accessible entry point into the later philosophy. It is shorter and more focused than the Philosophical Investigations, and its subject matter — knowledge, doubt, and certainty — is more immediately engaging than the questions about language and meaning that dominate the earlier work. The book can be read profitably by anyone interested in epistemology, and it requires no specialized training in philosophy. Its aphoristic form makes it suitable for browsing as well as for systematic study, and each reading tends to reveal new insights that were missed before. This is a book that rewards return visits, and its influence on contemporary epistemology continues to grow as philosophers find in its remarks new resources for thinking about the foundations of knowledge.

The book's lasting achievement is to have transformed the way philosophers think about the foundations of knowledge. Before On Certainty, the standard approach to epistemology was to ask what we know and how we know it — to seek the conditions under which a belief counts as knowledge. After On Certainty, it became possible to ask a different and more fundamental question: what are the certainties that underlie all our knowing and doubting, and what is their epistemic status? The idea that there is a bedrock of hinge certainty — not knowledge, not belief, but something else that makes both possible — has opened up new ways of thinking about skepticism, about the structure of justification, and about the relationship between knowledge and action.

For readers who want to engage with the contemporary literature on hinge epistemology, the work of Danièle Moyal-Sharrock, Duncan Pritchard, and Annalisa Coliva provides the most developed systematic accounts. Each of these philosophers offers a different interpretation of what the hinges are and how they function, and the debate among them is one of the most active areas in contemporary epistemology. The Stanford Encyclopedia of Philosophy entry on "Ludwig Wittgenstein" provides an overview of these interpretations, and the secondary literature on On Certainty is now extensive enough to support its own bibliographic guides.

These connections and further readings offer pathways into the broader philosophical landscape that surrounds on certainty.

Sources

1. Ludwig Wittgenstein, On Certainty, ed. G. E. M. Anscombe and G. H. von Wright (Oxford: Blackwell, 1969). The posthumous text of the late notebooks.
2. Stanford Encyclopedia of Philosophy, "Ludwig Wittgenstein." Situates On Certainty within the later philosophy and the hinge-proposition idea.
3. Internet Encyclopedia of Philosophy, "On Certainty." An accessible exposition of the hinge propositions, the critique of Moore, and the response to skepticism.