Relevance is a term used to describe how pertinent, connected, or applicable some information is to a given matter.

In politics

During the 1960s, relevance became a fashionable buzzword, meaning roughly 'relevance to social concerns', such as racial equality, poverty, social justice, world hunger, world economic development, and so on. The implication was that, e.g., the study of medieval poetry and the practice of corporate law were not worthwhile because they did not address pressing social issues. The 1960s decade refers to the years from January 1, 1960 to December 31, 1969, inclusive. ... A buzzword (also known as a fashion word or vogue word) is an idiom, often a neologism, commonly used in managerial, technical, administrative, and sometimes political environments. ... This article needs cleanup. ... A boy from an East Cipinang trash dump slum in Jakarta, Indonesia shows his find. ... Social justice refers to conceptions of justice applied to an entire society. ... A famine is a social and economic crisis that is commonly accompanied by widespread malnutrition, starvation, epidemic disease and increased mortality. ... Economic development is the development of the economic wealth of countries or regions for the well-being of their inhabitants. ... Medieval poetry was often preserved by mere happenstance. ... Corporations law or corporate law is the law concerning the creation and regulation of corporations. ...

In logic

Main article: relevance logic

In formal reasoning, relevance has proved an important but elusive concept. It is important because the solution of any problem requires the prior identification of the relevant elements from which a solution can be constructed. It is elusive, because the meaning of relevance appears to be difficult or impossible to capture within conventional logical systems. The obvious suggestion that q is relevant to p if q is implied by p breaks down because under standard definitions of material implication, a false proposition implies all other propositions. However though ‘iron is a metal’ may be implied by ‘cats lay eggs’ it doesn’t seem to be relevant to it the way in which ‘cats are mammals’ and 'mammals give birth to living young’ are relevant to each other. Relevance logic, also called relevant logic, is any of a family of non-classical substructural logics that impose certain restrictions on implication. ... In logical calculus of mathematics, the logical conditional (also known as the material implication, sometimes material conditional) is a binary logical operator connecting two statements, if p then q where p is a hypothesis (or antecedent) and q is a conclusion (or consequent). ...

More recently a number of theorists have sought to account for relevance in terms of “possible world logics”. Roughly, the idea is that necessary truths are true in all possible worlds, contradictions (logical falsehoods) are true in no possible worlds, and contingent propositions can be ordered in terms of the number of possible worlds in which they are true. Relevance is argued to depend upon the “remoteness relationship” between an actual world in which relevance is being evaluated and the set of possible worlds within which it is true. Modal logic, or (less commonly) intensional logic is the branch of logic that deals with sentences that are qualified by modalities such as can, could, might, may, must, possibly, and necessarily, and others. ... Philosophers generally consider logical possibility to be the broadest sort of subjunctive possibility in modal logic. ... Broadly speaking, a contradiction is an incompatibility between two or more statements, ideas, or actions. ... In philosophy and logic, contingency is the status of facts that are not logically necessary. ...

Interesting as this approach might be, it seems to have little to do with the relevance judgements made in practical problem solving by plumbers and the rest of humankind.

In economics

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. Specifically, Keynes proposed that new evidence e is irrelevant to a proposition, p given old evidence q, if and only if p/q & e = p/q and relevant otherwise. Paul Samuelson, Nobel Prize in Economics winner. ... John Maynard Keynes (right) and Harry Dexter White at the Bretton Woods Conference John Maynard Keynes, 1st Baron Keynes, CB (pronounced canes, IPA ) (5 June 1883 – 21 April 1946) was a British economist whose ideas, called Keynesian economics, had a major impact on modern economic and political theory as well...

Unfortunately, there are serious technical problems with this definition, for example the relevance of piece of evidence turns out to be sensitive to the order in which all pieces of evidence were received.

In cognitive science and pragmatics

Further information: Relevance theory

In 1986, Dan Sperber and Deirdre Wilson drew attention to the central importance of relevance decisions in reasoning and communication. They proposed an account of the process of inferring relevant information from any given utterance. To do this work, they used what they called the “Principle of Relevance”: namely, the position that any utterance addressed to someone automatically conveys the presumption of its own relevance. The central idea of Sperber and Wilson’s theory is that all utterances are encountered in some context, and the correct interpretation of a particular utterance is the one that allows most new implications to be made in that context on the basis of the least amount of information necessary to convey it. 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. There are two ways to conceive of how thoughts can be communicated from one person to another. ... Dan Sperber is a French anthropologist, linguist and cognitive scientist, currently a Research Director at the Jean Nicod Institute, CNRS. He is known, amongst other things, for his work on pragmatics and in particular relevance theory; and also for his theory on “epidemiology of representations”. In the early Seventies, Sperber...

Sperber and Wilson stress that this theory is not intended to account for every intuitive application of the English word "relevance". Relevance is restricted to relationships between utterances and interpretations, and so the theory cannot account for intuitions such as the one that relevance relationships obtain in problems involving physical objects. If a plumber needs to fix a leaky faucet, for example, some objects and tools are relevant (i.e. a wrench) and others are not (i.e. a waffle iron). And, moreover, the latter seems to be irrelevant in a manner which does not depend upon the plumber’s knowledge, or the utterances used to describe the problem.

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 key feature of their theory is the idea that relevance is goal-dependent. An item (e.g., an utterance or object) is relevant to a goal if and only if it can be an essential element of some plan capable of achieving the desired goal. This theory embraces both propositional reasoning and the problem-solving activities of people such as plumbers, and defines relevance in such a way that what is relevant is determined by the real world (because what plans will work is a matter of empirical fact) rather than the state of knowledge or belief of a particular problem solver.

References

• Gorayska B. & R. O. Lindsay (1993). The Roots of Relevance. Journal of Pragmatics 19, 301-323. Los Alamitos: IEEE Computer Society Press.
• Keynes, J. M. (1921). Treatise on Probability. London: MacMillan
• Lindsay, R. & Gorayska, B. (2002) Relevance, Goals and Cognitive Technology. International Journal of Cognitive Technology, 1, (2), 187-232
• Sperber, D. & D. Wilson (1986/1995) Relevance: Communication and Cognition. 2nd edition.

Oxford: Blackwell.

• Sperber, D. & D. Wilson (1987). Précis of Relevance: Communication and Cognition. Behavioral and Brain Science, 10, 697-754.
• Zhang, X, H. (1993). A Goal-Based Relevance Model and its Application to Intelligent Systems. Ph.D. Thesis, Oxford Brookes University, Department of Mathematics and Computer Science, October, 1993.