The Coherence Theory of Truth
Chapter Fourteen
Syllabus topic 1.5, "Three Theories of Truth (Western perspectives)."
Pages 67 to 71 of 334
In one line
A proposition is true when it fits consistently into a system of other propositions that are accepted.
In the wording a student can write in an examination: on the coherence theory, truth consists in a relation between a proposition and other propositions rather than between a proposition and the world. A proposition is true if and only if it coheres with a specified body of propositions, coherence requiring at least logical consistency and usually mutual support as well.
Why anybody holds it
The theory begins from the last objection to the correspondence theory, and that objection is a serious one. To check whether a proposition corresponds to a fact you would have to compare the proposition with the world directly, standing outside all your own beliefs while you did it. Nobody can do that. Every check we actually perform is a comparison of one proposition with others, including the propositions that record our observations.
So, says the coherence theorist, if comparison with the world is impossible in practice, and comparison with other propositions is what we in fact do, why not say that this is what truth consists in?
The theory also matches something real about how belief works. A single claim is almost never assessed on its own. It is assessed by asking whether it can be fitted into everything else we take ourselves to know, and a claim that cannot be fitted in is rejected without further investigation.
The theory stated properly
A proposition is true if and only if it coheres with a specified system of propositions.
Two things have to be filled in before the theory says anything definite.
What is the system? Different versions answer differently, and the differences matter. It may be the beliefs of the person judging, or the beliefs of most people in that society, or the beliefs of the informed, or the ideal complete system of all true propositions. The last is the version rationalist philosophers such as Leibniz, Spinoza, Hegel and Bradley worked with.
What is coherence? At a minimum, logical consistency: a proposition that contradicts the system is out. Most versions ask for more than that, namely mutual support, so that the propositions explain and reinforce one another rather than merely sitting side by side without conflict. The strongest versions require that each true proposition logically implies the others.
Where courts reason this way
A court cannot compare testimony with the past. The past is gone, and there is nothing left of it to hold the testimony against. What the court has is a body of other material, and the assessment of any one witness is overwhelmingly an assessment of fit.
Consider how a witness is actually disbelieved. Rarely because the judge saw the event. Usually because the account does not hang together: it is internally inconsistent, or it contradicts a document, or it is inconsistent with the admitted movements of the parties, or it requires a sequence of events that could not have occupied the time available. Every one of those is a coherence test.
The Coherence Theory of Truth
The same reasoning drives circumstantial evidence, corroboration, and the treatment of a defence as an afterthought because it was raised late and does not sit with the earlier conduct.
But notice how far the law refuses to go. A story that hangs together perfectly is not thereby true, and every court knows it, because a fabricated account is constructed precisely so as to hang together. Coherence is treated as evidence of truth and never as the definition of it. That refusal is the coherence theory's chief difficulty, met in a courtroom every day.
The criticisms
Two rival systems may each be coherent. The plaintiff's case and the defendant's case are each, at their best, complete and internally consistent stories. If coherence is truth, both are true, and they contradict each other. The theory then collides with the law of contradiction, which is a very high price.
Truth becomes relative to a system. A proposition may cohere with my beliefs and not with yours, so it is true for me and false for you. If "true for me" means true, this is again a contradiction. Most philosophers prefer to keep the law of contradiction and drop the theory. As the previous chapter's distinction suggests, someone who says "that is true for me" is almost always saying only "I believe it".
Coherence with what? If the system is the beliefs of a society, then a society that agreed the earth was flat would have made it flat, which nobody accepts. If the system is the ideal set of all true propositions, the theory has explained truth by using the notion of truth, which is circular.
A consistent fiction is still fiction. A well constructed novel is internally coherent throughout and no part of it is true. This is the objection in its shortest form and it is the one to write down.
A worked example
Two accounts are given of the same evening.
The plaintiff's account. He handed over Rs 2,00,000 in cash at the defendant's shop at about seven in the evening; the defendant counted it and promised to repay in six months; the plaintiff then went home and told his wife.
The defendant's account. No money was handed over at all; the plaintiff came to the shop about an unrelated matter; the suit is an afterthought following a family quarrel.
The Coherence Theory of Truth
Each account is internally consistent. Each explains why the plaintiff was at the shop. Neither contains a contradiction.
How the court proceeds. It looks for the points at which each account has to meet something independently fixed. Was Rs 2,00,000 withdrawn from any account that week? Does the shop's own record show the plaintiff's visit? Was the family quarrel before the alleged loan or after it? What did the plaintiff say in his notice, and does the notice fit his evidence?
What this shows about the theory. The court is testing coherence, and testing it against a wider and wider body of material until one account fails to fit. That is the coherence theory as a method. But the court's justification for the method is a correspondence assumption: it believes the wider body of material to be connected to what actually happened, and that is why fitting with it is worth anything. Take the correspondence assumption away and the exercise is only a comparison of two fictions.
The honest summary, and the one that earns marks: coherence is an excellent test of truth and a poor definition of it.
Distinctions that carry marks
| Correspondence | Coherence | |
|---|---|---|
| Truth is a relation to | The world | Other propositions |
| What is compared | Proposition and fact | Proposition and system |
| Can all our beliefs be false? | Yes | Not on most versions |
| Chief strength | It is what we ordinarily mean | It describes how we actually check |
| Chief weakness | Comparison with the world cannot be performed | A consistent fiction comes out true |
| Test of truth | Definition of truth | |
|---|---|---|
| What it does | Tells us how to find out | Tells us what truth is |
| Coherence as | Excellent | Poor |
| The distinction matters because | A good test may rest on a different definition | Confusing them is the standard error in this topic |
What this does not mean
Coherence is not mere consistency. Two unrelated propositions that do not contradict each other are consistent and not coherent. Coherence requires positive support among the members of the system.
The theory is not "truth is what people agree on". That is a cruder view. The coherence theorist demands a logically organised system, not a show of hands, although the version that fills the blank with the beliefs of a society comes close to it.
Rejecting the theory does not mean rejecting the method. Courts, historians and detectives all use coherence to decide what to believe, and are right to. What they do not do is define truth by it.
Quick revision
Statement: a proposition is true if and only if it coheres with a specified system of propositions.
Motivation: we can never compare a proposition with the world directly, only with other propositions.
The Coherence Theory of Truth
Two blanks to fill: which system, and what coherence requires. Coherence needs at least consistency and usually mutual support.
Advocates: Leibniz, Spinoza, Hegel, Bradley, Blanshard and others in the rationalist tradition.
Criticisms: rival coherent systems; truth becomes relative and collides with the law of contradiction; coherence with what; a consistent fiction comes out true.
Legal use: the assessment of a witness is a coherence test. The law treats coherence as evidence of truth, never as its definition.
The line to write: coherence is a good test of truth and a bad definition of it.
Test yourself
1. State the coherence theory and identify what has to be specified before it says anything definite.
A proposition is true if and only if it coheres with a system of other propositions. Two things must be specified. First, which system: one's own beliefs, the beliefs of one's society, the beliefs of the informed, or the ideal complete set of true propositions. Second, what coherence requires: at a minimum logical consistency, on most versions mutual support, and on the strongest versions mutual entailment.
2. What objection to the correspondence theory motivates the coherence theory?
That we cannot compare a proposition with the world directly. To do so we would have to step outside all our beliefs and inspect reality unmediated, which nobody can do. Every check that is actually carried out compares one proposition with others, our records of observation included. The coherence theorist concludes that if comparison with other propositions is all we ever do, that is what truth must consist in.
3. Give the strongest criticism of the theory and explain it.
A well constructed fiction is internally coherent throughout, and every part of it is false. More sharply, in litigation each side's case at its best is a complete and consistent story, so if coherence were truth both would be true and they contradict one another. The theory then violates the law of contradiction, which most philosophers are unwilling to give up for any theory of truth.
4. How do courts use coherence, and where do they stop?
They use it constantly to assess evidence: a witness is disbelieved because the account is internally inconsistent, or conflicts with a document, or cannot be fitted into the admitted movements of the parties or the time available. They stop at the point of definition. No court holds that a coherent story is thereby true, precisely because a fabricated account is built to be coherent, so coherence is treated as evidence of truth and never as truth itself.
5. Distinguish a test of truth from a definition of truth.
A test tells you how to find out whether a proposition is true; a definition tells you what its being true consists in. The two need not be the same, and here they are not: coherence is an excellent test, because a proposition that will not fit with anything else we know is almost always false, and a poor definition, because fitting with other propositions is not what we mean when we call something true.
The Coherence Theory of Truth
6. Why does the coherence theory tend towards relativism?
Because a proposition may cohere with one person's or one group's system and not with another's, so the theory yields that it is true for the first and false for the second. If "true for me" is taken to mean true, the same proposition is both true and false, which the law of contradiction forbids. The usual conclusion is that the phrase "true for me" is a loose way of saying "believed by me", and that truth itself is not relative in this way.
The rest of this subject
These notes are cut from the University's printed syllabus. Open the syllabus itself, or the past papers, for the same subject.