Jourdain’s paradox (1913)

Named after its discoverer, the mathematician Philip Edward Bertrand Jourdain (1879-1919). The paradox is equivalent to the sentence ‘The second part of this sentence is true and the first part of this sentence is false’, which contradicts itself whether the first half is true or not. However, the halves of the sentence refer indirectly

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Justice

Theory of the morally appropriate way of resolving social differences. There is no one theory of justice. One view is that justice involves avoiding or preventing harm to people; another that it involves treating people according to their deserts; another that people should be treated according to their needs; another that they should be

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Language of thought

Theory developed by Jerry A Fodor, though going back to the English philosopher William of Ockham (c. 1285-1349). It seeks to explain thinking by postulating a hypothetical language of thought (or mentalese) such that to have a belief or desire and so on is to be related in certain ways to one or more sentences

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Lawyer paradox (5TH CENTURY BC)

Ascribed to the sophist philosopher Protagoras(c.490-420 BC). A lawyer teaches law to a student without fee on condition that the student will pay him when he qualifies and wins his first case. However, when the student qualifies he takes up another profession. The lawyer sues him for his fees, on the grounds that if he

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Legal positivism

Doctrine (or set of doctrines) stemming primarily from English jurist John Austin (1790-1859) in his The Province of Jurisprudence Determined (1832). It emphasizes what the law actually is rather than what it should be: it cannot, like natural law, be defined by reference to its content, but is what is commanded by the sovereign.

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Leibniz’s law

Name often given to either or both of the identity of indiscernibles and the indiscernibility of identicals; called after German philosopher and mathematician Gottfried Wilhelm Leibniz (1646-1716). Leibniz himself seems to have held explicitly only the first, and to have treated it sometimes as necessary and sometimes as contingent. Source: H G Alexander, ed.. The Leibniz-Clarke Correspondence (1956) Leibniz’ law may

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Principle of limited independent variety

Principle adopted by English economist John Maynard Keynes (1883-1946) to underpin his Bayesian approach to induction by finding a justification for assigning the relevant probabilities. The principle says that, for at least that sphere we are investigating, the number of objects and qualities it contains may be infinite, but the number of independent groups into which

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Linguistic phenomenology

Name sometimes used for the detailed and careful analysis of ordinary language undertaken by linguistic philosophy. Though not unconnected with ordinary phenomenology – especially in the work of English philosopher Gilbert Ryle (1900-1976) – it was an empirical rather than an a priori study, and did not involve ‘bracketing’ the world. Source: G Ryle, Collected Papers, 1 (1971)

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Linguistic philosophy

Linguistic philosophy Also called ordinary language philosophy. A philosophical movement arising after World War II and lasting until the early 1960s (not to be confused with the philosophical subject called philosophy of language). A leading exponent was John Langshaw Austin(1911-1960). Partly as a reaction against the constraints of logical positivism, and influenced by Ludwig Wittgenstein’s (1889-1951) slogan

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Local sign theory

Theory, originated by German philosopher Rudolph Hermann Lotze (1817-1881), that we assign a bodily location to the cause of a bodily sensation (for example, we come to treat a pain as ‘in’ our right hand) because of a special quality which the sensation has. This special quality we come to associate with the location of its

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Logical atomism

Theory, held briefly by Bertrand Russell (1872-1970) and Ludwig Wittgenstein (1889-1951) soon after World War I, that a proper description of reality would be in terms of atomic propositions, each containing a word standing for a quality or relation and one or more words standing for objects which had the quality or relation. The objects must be basic

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Logical empiricism

Version of empiricism applying to the meanings of words or sentences, whereby they have meaning only if there are rules involving sense-experience for applying or verifying them; the rules may also constitute the meaning. (Analytic sentences – that is, roughly, those made true or false by logical considerations – are excepted.) Akin to, though some say

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Logical positivism

A 20th century development of positivism which emphasizes questions of language and meaning and the role of logical relations like entailment. It originated in the Vienna Circle and continued mainly in English-speaking countries (with Holland and Scandinavia) until World War II, after which it was replaced by linguistic philosophy in Britain and various movements in the USA and elsewhere. Its

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Logical relation theory of probability

Theory due especially to English economist John Maynard Keynes (1883-1946) in his Treatise on Probability (1921), Chapter 1. It says that the probability of a hypothesis is a logical relation (rather like logical entailment, only weaker) between a hypothesis and a body of evidence for it. Probability is thus made relative to evidence. This could be

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Logicism

Theory, due to Gottlob Frege (1848-1925) and Bertrand Russell (1872-1970), that the concepts and theories of mathematics (in particular of arithmetic) can be derived from those of logic. This, if feasible, would support logical positivism and reductionism in general. Arithmetic was in fact reduced to set theory – developed by Georg Cantor (1845-1918) – as a first step, but set theory

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Manicheism

Religious system founded by Mani of Persia (c. AD 215-76) and emphasizing fundamental dualism of good and evil as independent principles, represented by spirit and body and symbolized by light and dark. Sometimes treated as a Christian heresy, Manicheism is rather a separate religion with its roots in Zoroastrianism (founded by Zoroaster (or Zarathustra)

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Materialism

Any theory emphasizing the existence, priority, or value of matter or material objects; though the popular sense of emphasizing the value of material things is uncommon in philosophy. Usually materialists say that matter alone exists, everything else (notably minds or spirits and their ideas and experiences) being analyzable in terms of matter (a form

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Doctrine of the mean

The doctrine of Aristotle (384-322 BC) that moral virtue can be defined as a disposition concerned with choice and lying in a mean. Any given virtue lies between two extremes, for example courage lies in a mean between rashness and cowardice. The mean, however, is not an arithmetical mean, but is ‘relative to us’; that is,

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Theories of meaning (traditional)

Discussed BC in both Greek philosophy and Indian linguistics. Much theoretical progress in latter half of the 20th century. An elusive concept which has been theorized from many different perspectives: meaning as use, as behaviour, as intention, as concepts, as images, as truth-conditions, and so on. It is best to disperse the term into

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Mechanism

As a theory, rather than a device, the view that everything happens mechanically; that is, everything can ultimately be explained in terms of certain laws of nature which apply to the behavior of matter in motion, as in the popular example of clockwork. Ideally the laws should require as few terms as possible –

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