On Certainty

Context and Composition

On Certainty (Über Gewißheit) is a late work by Ludwig Wittgenstein, composed between 1950 and 1951 and published posthumously in 1969. It consists of numbered remarks, not a continuous treatise, and reflects Wittgenstein’s mature engagement with issues in epistemology, especially skepticism and the nature of knowledge.

The immediate stimulus for the work was G. E. Moore’s attempt to refute skepticism by appealing to apparently obvious truths such as “Here is a hand” or “The earth has existed for many years.” Moore argued that such propositions are things we know with certainty and that their truth disproves radical skeptical claims. Wittgenstein’s remarks, while often sympathetic to Moore’s starting point, critically examine what it means to say that one “knows” such things, and what role these propositions play in our language and practices.

On Certainty is generally regarded as belonging to Wittgenstein’s late period, continuous with the concerns of the Philosophical Investigations. Rather than constructing a theory of knowledge, Wittgenstein investigates the grammar and use of concepts like “know,” “doubt,” and “certainty” within ordinary language.

Hinge Propositions and the Limits of Doubt

One of the most influential ideas in On Certainty is that of hinge propositions (often called hinges). These are propositions that:

• are not usually doubted or justified in practice,
• form the background against which meaningful doubt and knowledge-claims arise,
• are more akin to rules of a language-game or framework assumptions than to empirical hypotheses.

Examples include: “The world has existed for a long time,” “I have never been on the moon,” or “There are physical objects.” Such claims are not typically treated as items of knowledge supported by evidence, nor as empirical conjectures to be tested. Instead, they are taken for granted in the course of inquiry, evidence-gathering, and everyday action.

Wittgenstein argues that doubt is only intelligible within a framework of things not doubted. To doubt everything at once would dissolve the very distinction between doubting and not doubting. Thus, radical skepticism—questioning the existence of the external world as a whole—misunderstands the logic of doubt. Doubting presupposes some certainties that “stand fast” and give doubt its point.

These hinge propositions function as logical or grammatical conditions for practices of reasoning and knowing, rather than as conclusions of those practices. They “lie apart from the route travelled by inquiry,” yet they shape that route. This position allows Wittgenstein both to acknowledge the attraction of Moore’s examples and to deny that they are properly described as items of knowledge in the ordinary sense.

Knowledge, Justification, and Practice

A central target of On Certainty is a misleading picture of knowledge as a mental state grounded in absolute foundations. Wittgenstein examines ordinary uses of “I know…” and contends that such uses are governed by public criteria and language-games, not by an inner act of grasping certainty.

Several key themes emerge:

1. The Grammar of “Knowing”
   Wittgenstein emphasizes that “know” has a distinctive grammar: to say “I know” typically implies that doubt is possible and has been, or could be, resolved. Saying “I know that this is a hand” in Moore’s sense, where doubt is not coherently in play, mislocates the expression in a language-game where it does not naturally belong.

2. Certainty Without Evidence
   Many certainties do not rest on evidence or inference, yet they are not arbitrary. They are woven into forms of life—the complex patterns of human practice, upbringing, and shared language. For instance, trusting that the world existed before one’s birth usually does not arise from a chain of proofs; it is a condition of acquiring and using concepts like “before,” “age,” or “history.”

3. The Role of Training and Social Practices
   Wittgenstein highlights training, custom, and education as central to how certainties are transmitted. Children are not given proofs that there is an external world; rather, they are taught to navigate it. In this way, the “foundations” of knowledge are located not in an indubitable inner realm but in public, shared practices.

4. Relativity and Stability of Hinges
   While hinges are remarkably stable within a given community and historical situation, Wittgenstein allows that some such commitments may vary across contexts and cultures. This has led some interpreters to read On Certainty as suggesting a kind of framework-relativism, though the extent of such relativity is debated.

Through these analyses, Wittgenstein reframes epistemological questions: rather than asking how knowledge is built upon secure foundations, he investigates how language and practices already presuppose a background of certainties that are neither justified nor unjustified in the usual sense.

Reception and Influence

Since its publication, On Certainty has become a key text in contemporary epistemology and Wittgenstein studies. Its influence can be seen in several areas:

• Hinge Epistemology: Philosophers such as Peter Strawson, Duncan Pritchard, Annalisa Coliva, and others have developed “hinge epistemology,” exploring how Wittgenstein’s hinges might provide a response to skepticism without restoring classical foundationalism.

• Responses to Skepticism: Many have interpreted Wittgenstein as offering a “quietist” or therapeutic dissolution of skeptical problems, arguing that radical doubt misuses our ordinary concepts. Others see in On Certainty resources for contextualist or externalist accounts of knowledge.

• Comparisons with Moore and Descartes: The work is now standard reading alongside Moore’s anti-skeptical essays and Descartes’ Meditations, as it reframes both projects. Instead of refuting skepticism with counter-arguments, Wittgenstein interrogates the presuppositions shared by skeptic and anti-skeptic alike.

• Philosophy of Language and Practice: On Certainty further develops the later Wittgenstein’s emphasis on language-games and forms of life, extending it to questions of evidence, rationality, and the limits of justification.

Critics have raised questions about whether Wittgenstein’s account can distinguish adequately between rational and irrational certainties, or whether it risks a conservative endorsement of existing practices. Others dispute how far the notion of hinges can be systematized into a positive epistemological theory, given Wittgenstein’s resistance to theory-building.

Despite such debates, On Certainty is widely regarded as a major contribution to 20th‑century philosophy, notable for transforming the way philosophers think about certainty, doubt, knowledge, and the background conditions of understanding. It continues to shape discussions of skepticism, the nature of normativity, and the interplay between language, practice, and belief.