Relevance

It is elusive, because the meaning of relevance appears to be difficult or impossible to capture within conventional logical systems.

If one states "I love ice cream", and another person responds "I have a friend named Brad Cook", then these statements are not relevant.

In 1986, Dan Sperber and Deirdre Wilson drew attention to the central importance of relevance decisions in reasoning and communication.

For Sperber and Wilson, relevance is conceived as relative or subjective, as it depends upon the state of knowledge of a hearer when they encounter an utterance.

Sperber and Wilson stress that this theory is not intended to account for every intuitive application of the English word "relevance".

If a plumber needs to fix a leaky faucet, for example, some objects and tools are relevant (e.g. a wrench) and others are not (e.g. a waffle iron).

A theory of relevance that seems to be more readily applicable to such instances of physical problem solving has been suggested by Gorayska and Lindsay in a series of articles published during the 1990s.

The economist John Maynard Keynes saw the importance of defining relevance to the problem of calculating risk in economic decision-making.

He suggested that the relevance of a piece of evidence, such as a true proposition, should be defined in terms of the changes it produces of estimations of the probability of future events.

The implication was that some subjects, e.g., the study of medieval poetry and the practice of corporate law, were not worthwhile because they did not address pressing social issues.