On certainty

On Certainty (Über Gewißheit) is a set of 676 numbered remarks on knowledge, doubt and the things we never think to question. Wittgenstein wrote them in the last eighteen months of his life; the final entry is dated 27 April 1951, two days before he died in Cambridge. He never prepared them for print. G.E.M. Anscombe and G.H. von Wright edited the notebooks and published them in 1969, with an English translation by Denis Paul and Anscombe facing the German.

How the book came about

The starting point is G.E. Moore. In "A Defence of Common Sense" (1925) and "Proof of an External World" (1939), Moore claimed to know with certainty a list of plain truths: that he has two hands, that the earth existed long before his birth, that he has never been far from its surface. Holding up a hand, he said "here is one hand" and presented this as a refutation of the sceptic.

Wittgenstein admired Moore's stubbornness but thought he had misdescribed what he was doing. A visit to Norman Malcolm in Ithaca in 1949, where the two discussed Moore at length, seems to have set him writing. The remarks fall into four batches, the first probably written in Vienna around the turn of 1949-1950, the last in Cambridge in March and April 1951 in the house of his doctor, Edward Bevan.

What it says

Moore was right that these propositions are certain, Wittgenstein argues, but wrong to call this knowledge. "I know" belongs where it makes sense to ask "how do you know?" and where one could turn out to be mistaken. Nobody in ordinary circumstances checks whether they have two hands. That is not because the evidence is overwhelming, but because this certainty is not based on evidence at all. It is the background against which evidence counts as evidence.

Das heißt, die Fragen, die wir stellen, und unsre Zweifel beruhen darauf, daß gewisse Sätze vom Zweifel ausgenommen sind, gleichsam die Angeln, in welchen jene sich bewegen.

That is to say, the questions we raise and our doubts depend on the fact that some propositions are exempt from doubt, as it were the hinges on which those turn.

On Certainty §341

From this image comes the term hinge propositions. Other images do the same work: the riverbed that guides the water but can itself shift slowly (§§96-99), the axis that stays still because everything turns around it (§152). Doubt, Wittgenstein says, comes after belief. Someone who tried to doubt everything would not even get as far as doubting (§115), because the game of doubting already presupposes certainty. And justification ends somewhere: not in propositions that strike us as self-evident, but in what we do (§204).

The book also asks what happens when two whole systems of certainty meet, such as the scientist and the person who consults an oracle (§609). Here Wittgenstein suggests that at the end of reasons comes persuasion. Whether that makes him a relativist is one of the liveliest debates about the book.

How to read it

Read it in order, slowly, a few pages at a time. The remarks are short and the language is plain, so the difficulty lies in following a mind that keeps testing its own claims. Do not expect a thesis that is stated once and defended. Expect returns, revisions and sudden clear sentences.

The Paul and Anscombe translation has been standard for half a century. In 2025 Wiley-Blackwell published a new translation by P.M.S. Hacker with an introduction on how the text was assembled. The manuscripts themselves can be consulted through the Bergen Nachlass Edition. Some familiarity with language games and Philosophical Investigations helps, but is not required.

Why it matters

For decades On Certainty was read as a footnote to the Investigations. Since the 1990s it has become a central text in epistemology. Danièle Moyal-Sharrock speaks of a "third Wittgenstein", and authors such as Duncan Pritchard have built "hinge epistemology" on it as a response to scepticism. Interpreters disagree on whether hinges are propositions at all, or rather ways of acting that only look like propositions when we write them down. The Stanford Encyclopedia entry on certainty gives a sense of how wide the discussion has become.

Verdict

Read this if you want to see the late Wittgenstein at his most direct, or if you have ever wondered why radical doubt feels both irrefutable and absurd. It is the best second book after the Investigations, and for some readers a better first one. Skip it if you need a finished argument with a conclusion: what you get instead is philosophy in the act of being written, right up to the last days.