Hinge propositions

Hinge propositions are the certainties our questions and doubts turn on: "I have two hands", "the earth existed long before I was born", "I have never been to the moon". We do not check them, because checking anything at all depends on them. Wittgenstein worked the idea out in Über Gewißheit (On Certainty), the notes he wrote between 1949 and April 1951, the last of them two days before his death.

His central image is a door. A door can only swing if its hinges stay put. In the same way, inquiry, testing and doubting can only move if some things are not moved.

Das heißt, die Fragen, die wir stellen, und unsere 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

In the animation above, a door swings back and forth. The swinging is our questions and doubts: is the train on time, did I lock the door, is this mushroom safe? The hinges do not move. They carry labels such as "I have two hands" and "The earth existed long before my birth", examples taken from the English philosopher G.E. Moore. Two remarks later, Wittgenstein states the point in one line:

Wenn ich will, daß die Tür sich drehe, müssen die Angeln feststehen.

If I want the door to turn, the hinges must stay fixed.

On Certainty §343

Where does the idea come from?

The starting point was Moore. In "A Defence of Common Sense" (1925) he listed truisms he claimed to know with certainty, such as that the earth had existed for many years before his birth. In "Proof of an External World" (1939) he held up his hands and argued: here is one hand, here is another, so external things exist. The Stanford Encyclopedia entry on Moore describes both papers and their influence on Wittgenstein.

Wittgenstein returned to these papers in 1949, while staying with his former student Norman Malcolm in Ithaca, New York. Their conversations set off the notes that became On Certainty. The book opens with Moore's hand: if you do know that here is one hand, he writes, we will grant you all the rest (§1).

Was Moore right?

Yes and no. Wittgenstein agreed that Moore's sentences are not open to doubt. But he thought Moore was wrong to say he knew them. "I know" belongs where there could be grounds, checking and the possibility of error. You say "I know the meeting is at three" because you could have got it wrong. Saying "I know I have two hands" in normal circumstances is odd, not because it is false, but because there is nothing it would be an answer to. Moore's propositions are not pieces of knowledge resting on evidence. They are part of the framework in which evidence counts at all.

That is also Wittgenstein's reply to the radical sceptic, who wants to doubt everything:

Wer an allem zweifeln wollte, der würde auch nicht bis zum Zweifel kommen. Das Spiel des Zweifelns selbst setzt schon die Gewißheit voraus.

Whoever wanted to doubt everything would not even get as far as doubting. The game of doubting itself already presupposes certainty.

On Certainty §115

A doubt needs a background that is not in doubt: you can only wonder whether your watch is slow if you take for granted that clocks, hours and your own eyes are in order.

Are hinges fixed forever?

No. Wittgenstein compares our world-picture to a riverbed. The water of our thoughts flows over it, and the bed itself can shift over time, though much more slowly, and there is no sharp line between the water and the bed (§96-99). A striking example: several remarks treat it as obvious that nobody has ever been to the moon (for instance §106 and §286). Within twenty years of his death, that hinge was gone. What counts as a hinge depends on a form of life and on a period, not on a list of eternal truths.

Hinges are also not just beliefs we happen to hold. Justification comes to an end, he says, not in propositions that strike us as immediately true but in our acting, which lies at the bottom of the language game (§204). Our certainty shows in what we do: you get out of bed without testing whether the floor is there.

How do scholars read hinges?

Interpretation is lively and contested. The Internet Encyclopedia of Philosophy gives a good overview. Some main positions:

• Entitlement. Crispin Wright argues that we are rationally entitled to hinges without having evidence for them, because inquiry cannot get started otherwise.
• Non-epistemic certainty. Danièle Moyal-Sharrock holds that hinges are not propositions we know at all, but a practical, almost animal certainty that shows in how we act. She speaks of a "third Wittgenstein".
• Arational commitments. Duncan Pritchard treats hinges as commitments outside the space of reasons, so that they cannot be known, doubted or justified.
• Framework judgements. Annalisa Coliva sees them as rules of the frame that settle what counts as an empirical description.

Even the name is a matter of debate. Wittgenstein speaks of propositions that are "as it were" hinges; whether they are really propositions, with a truth value, is exactly what the readings disagree about.

An everyday example

A colleague says: "Are you sure the train station is still there? Maybe it was demolished overnight." You do not go and check. Not because you have proof, but because the doubt has no grip: nothing in your life gives it a reason. Now imagine that the news reports a gas explosion near the station. Suddenly the question makes sense, and you can investigate. The difference is not in how strongly you believe, but in whether there is a game of doubting to be played. The practical page on hinges and doubt works this out further.