identity, law of

One of the traditional three laws of thought, the other two being the laws of contradiction and excluded middle. ‘Everything is what it is and not another thing’, or (where ‘P’ is any proposition) ‘If P then P’. The English empiricist George Edward Moore (1873-1958) took the first quotation above as the motto for his book Principia Ethica (1903), attributing

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ideology

An ideology (/ˌʌɪdɪˈɒlədʒi/) is a set of beliefs or philosophies attributed to a person or group of persons, especially as held for reasons that are not purely epistemic,[1][2] in which “practical elements are as prominent as theoretical ones.”[3] Formerly applied primarily to economic, political, or religious theories and policies, in a tradition going back to Karl Marx and Friedrich Engels, more recent use treats the term as mainly

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impossibility of a gambling system, principle of the

Principle that a properly defined collective (see frequency theory of probability) will be random in a sense that makes it impossible to construct a system for predicting results with any greater probability than would be possible without the system. The principle was named by the German mathematician and philosopher Richard von Mises (1883-1953). The key condition is

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indifference, principle of

The fundamental principle of statistical theory that unless there is a reason for believing otherwise, each possible event should be regarded as equally likely. In this crude form, the principle leads to paradoxes because we can group the alternatives in different ways: the next flower I meet might be blue or red, so its

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internal relations, doctrine of

Doctrine that all relations are internal to their bearers, in the sense that they are essential to them and the bearers would not be what they are without them. Some relations are clearly internal in this sense (four would not be four unless it were related to two by being its square), and some

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limited independent variety, principle of

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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mean, doctrine of the

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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meaning, theories of

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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negation, performative theory of

Theory that analyzes negation in terms of a special kind of linguistic activity, negating or denying; so that to say, for example, ‘It’s not raining’ may indeed be (as anyone would agree in straightforward cases) to deny that it is raining, but is also to utter a sentence which gets its meaning from that

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new riddle of induction

“Grue and bleen” redirects here. For the linguistic term “grue”, used for translation from natural languages, see Distinction of blue and green in various languages. Grue and bleen are examples of logical predicates coined by Nelson Goodman in Fact, Fiction, and Forecast to illustrate the “new riddle of induction” – a successor to Hume’s original problem. These predicates are unusual because their application is time-dependent;

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Ockham’s Razor

Occam’s razor, Ockham’s razor, Ocham’s razor (Latin: novacula Occami), or law of parsimony (Latin: lex parsimoniae) is the problem-solving principle that “entities should not be multiplied without necessity”,[1][2] or more simply, the simplest explanation is usually the right one. The idea is attributed to English Franciscan friar William of Ockham (c. 1287–1347), a scholastic philosopher and theologian who used a preference for simplicity to defend the idea of divine miracles. This philosophical razor advocates that

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organic unities, principle of

Principle that a whole may have a value which is different from, and not predictable on the basis of, the values of its parts. The attractiveness, for example, of a picture cannot normally be predicted from that of each color-patch taken separately. The principle was made much of by George Edward Moore (1873-1958), who distinguished his

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parsimony, principle of

Also called Ockham’s Razor. Principle that one should not multiply entities unnecessarily, or make further assumptions than are needed, and in general that one should pursue the simplest hypothesis. Adoption of this principle, though seemingly obvious, leads to problems about the role of simplicity in science, especially when we are choosing between hypotheses that are

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perfection, principle of

Also called the principle of the best. Principle of German philosopher and mathematician Gottfried Wilhelm Leibniz (1646-1716) that the actual world is the best of all possible worlds. Bertrand Russell (1872-1970) argued that Leibniz did not fully distinguish this principle from that of sufficient reason. Source: B Russell, A Critical Exposition of the Philosophy of Leibniz (1900), §§14-15 Perfection is a

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plenitude, principle of

Principle that if the universe is to be as perfect as possible it must be as full as possible, in the sense that it contains as many kinds of things as it possibly could contain. The world of nature must be as rich as possible. This is connected with the idea, used by St

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pre-established harmony, doctrine of

Doctrine primarily associated with Gottfried Wilhelm Leibniz (1646-1716) that there is no causation in the world but that each event arises when it does because it was pre-programmed to do so by God when the universe began. The doctrine is often illustrated by the image of the two clocks -attributed to Arnold Geulincx (1625-1669) – which keep perfect

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reducibility, axiom of

Axiom introduced by English philosopher and mathematician Bertrand Russell (1872-1970) in connection with the ramified theory of types. It says that any higher-order property or proposition can be reduced to an equivalent first-order one. The ramified theory caused difficulties for defining real numbers (using Dedekind sections) and for the process known as mathematical induction (roughly: if a property belongs

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relevant alternatives, theory of

Theory used in defending fallibilism against the charge that it leads to skepticism. Where P and Q are propositions, P counts for this purpose as an alternative to Q if it is inconsistent with Q, and counts as a relevant alternative if to know that Q we must also know that not-P. Variant formulations exist, but the

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semantics, truth-conditional

A variant of the correspondence theory, and akin to the redundancy theory. It was developed by the Polish logician Alfred Tarski (1902-1983), and applied to language by British philosopher Donald Davidson. (Also see: MONTAGUE GRAMMAR.) Semantic theory for sentences rather than words (also see: LEXICAL SEMANTICS). We know the meaning of a sentence if we know the

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speciation, theory of

(18TH CENTURY) Also called geographic speciation, this theory is most often associated with Ernst Mayr (1904- ), an evolutionary biologist at Harvard University (although many other biologists have theorized on the subject). It asserts that new species arise among sexually reproducing organisms because geographic isolation enables a small subgroup to diverge genetically from the

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