Coherence

The coherence theory of truth holds that a statement is true when it fits without contradiction into an existing system of statements. Truth becomes a relation inside the system. Its weakness is that a consistent system can be consistently wrong.

Coherentism explains justification by the mutual support of beliefs rather than by a foundation. Nothing is basic; everything is held by everything else. It is the alternative to grounding beliefs in something indubitable.

Consistency is the absence of logical contradiction within a set of statements. It is necessary and far from sufficient. Two unrelated true statements are consistent and support each other not at all.

A belief system is the whole of what a person accepts. Coherence is a property of that whole rather than of single statements. Changing one statement changes what the others are worth.

Explanatory coherence measures how well statements support each other by explaining one another. It is stronger than consistency because it requires a relation rather than the absence of conflict. It is the form of coherence that does real work.

The correspondence theory defines truth as agreement between a statement and what it is about. It is the competitor to the coherence theory. The two are better read as answering different questions.

The Münchhausen trilemma states that any chain of justification ends in infinite regress, circularity or an arbitrary stopping point. It is the argument that motivates coherentism. Coherentism accepts the circle and asks whether it is virtuous.

Comprehensiveness is the degree of completeness and breadth of a system. A narrow system is easier to keep coherent and explains less. The trade-off between coherence and scope is the practical problem.

It stays with qualitative notions: fit, consistency, mutual support. It leaves out every measure that would let coherence be calculated, the formal machinery for revising beliefs, and the conditions under which coherence is evidence of truth rather than of a well-built error.

Probabilistic coherence expresses fit as a relation between probabilities rather than as an impression. Without the probabilistic version there is no way to say that one system is more coherent than another.

The Shogenji measure quantifies coherence by comparing the joint probability of statements with what it would be if they were independent. A measure exists and has for decades.

The Olsson measure describes coherence through the overlap of the contents of beliefs. It is one of several competing formal proposals.

The Fitelson measure links confirmation theory to the measurement of coherence. It ties how much statements support each other to how much evidence raises their probability.

Epistemic circularity is the use of a source to vindicate that same source. Epistemic circularity is common, subtle and rarely noticed.

Mutual support is the reciprocal justification of single statements within a system. The term captures what coherentism actually claims.

Synergistic justification is the effect by which several weak pieces of evidence together yield a stronger warrant than their sum. It is also the mechanism behind most real-world confidence.

The bootstrapping problem concerns a source that confirms itself by its own outputs. Every system that measures its own success by its own instruments faces it.

Reciprocal evidence is the mutual raising of credibility between two assumptions. It is the point where mutual support becomes indistinguishable from mutual reinforcement of an error.

Non-contradiction is the explicit logical requirement that a system not assert a statement and its negation. Without it, coherence is a matter of taste.

Defeasibility is the property of coherent systems to be revisable when new information arrives. A system that cannot be revised is not coherent but closed.

Epistemic conservatism holds that an existing belief has some justification merely by being held. It explains why coherent systems resist correction even when the correction is right.

Belief revision is the formal restructuring of a system when new information is taken in. It is the operation that coherentism needs and never specifies.

The AGM postulates define normative axioms for the rationally minimal correction of a body of knowledge. They state what a good revision looks like.

Doxastic logic models belief formally with operators. It allows statements about what somebody believes to be evaluated.

Abduction is inference to the best explanation, the move that produces explanatory coherence. It is the engine behind the concept. Without it, explanatory coherence describes a result with no process.

Bayesian confirmation theory calculates how much evidence raises credibility, using Bayes's theorem. It is the quantitative counterpart to everything qualitative here.

Coherence-based reasoning is the cognitive process by which people resolve information by maximising fit. It describes what minds actually do. It also explains why coherent misinformation is unusually persuasive.

If people judged probability by logic, nobody would rate "bank teller and feminist" above "bank teller". Most did, because the longer story fits the description better.

Subjective probability measures a person's degree of belief in a statement. It is the quantity the formal measures operate on. Without it, degrees of belief cannot enter the account at all.

Constraint satisfaction is the mathematical procedure for solving systems of competing requirements. It is how coherence maximisation is computed.

Theory-ladenness is the fact that observations are shaped by the theoretical assumptions of the observer. It is the reason a coherent system can absorb contradicting observations without noticing.

Epistemic logic studies operators for knowledge and justification. It supplies the formal vocabulary for the claims made informally here.

Independence of sources is the condition under which their agreement is evidence. Two witnesses who copied each other agree perfectly and add nothing. Coherence without independence measures propagation rather than truth.

Textual coherence concerns whether a text makes sense as a whole, which is distinct from epistemic coherence. A well-written text can be internally coherent and epistemically empty.

Legal procedure uses coherence checks to assess testimony and evidence. It is an applied and refined version of the concept.

Social psychology examines how people adjust attitudes to remove internal tension. It describes the same mechanism from the outside. The adjustment is usually made to the belief that is cheapest to change, not to the one that is wrong.

Sociology examines how actors make events cohere into a meaningful account. It treats coherence as something produced rather than found. That reading explains a great deal about how public narratives form.

Ten results that agree with each other are coherent. If they were written from each other, the agreement is propagation rather than evidence. Independence is what turns agreement into a reason, and a result page does not show it.