The word theory comes from the Greek word theorein , which means “to contemplate, to observe, to examine”. In the language running, a theory is a Idée or a knowledge Spéculative, often based on the observation or the experiment, giving an ideal representation, moved away from the applications. Sometimes the theory term is employed to indicate something of temporary or not completely true, or in its Greek direction of a Députation which one sent to assist with the Olympic Games or the Oracle, a group of people even of objects: “a theory of small cries” (Amélie Nothomb).

Mathematics

When one formalizes the Mathématiques, in Logique mathematics, a theory is a whole of assertions of which some are Axiome S and the others of the demonstrable Théorème S starting from these axioms and by means of rules of logical. The first theorem of incomplétude of Gödel declares that any coherent theory, having a finished number of axioms (or diagrams of axioms) in a language which makes it possible to describe the Arithmétique, and which shows some simple arithmetic statements, will always contain proposals Indécidable S, i.e. proposals which the theory makes it possible neither to show nor to refute (by using of course only the axioms of this theory). It is the case of the Arithmétique of Peano but also of the set theory.

Sciences

In Science S, a theory is a model or a framework of work for the comprehension of nature and the human one. In Physical, the term of theory generally indicates the support mathematical, derived from a small unit from basic principles and equations, making it possible to produce experimental forecasts for a given category of physical systems. An example is the “electromagnetic theory”, usually confused with the traditional electromagnetism, and whose specific results are obtained starting from the Maxwell's equations.

The “theoretical” adjective associated with the description of a phenomenon often states that a particular result was predicted by a theory but that it was not observed yet. For example, until recently, the black holes were still regarded as theoretical objects. It is not rare in the history of physics that theories produced such forecasts and that it is only later that these last were confirmed by the experiment (for example: the Laser mathematically predicted in 1917 by Albert Einstein and realized only in 1953).

So that a theory is regarded as belonging to established knowledge, it is usually necessary that this one produces a critical experiment, i.e. an experimental result which was not prédictible by any other established theory.

• If the consequences envisaged are not contradicted by reality observed and measured, then the theory and its principles are consolidated.

• If remarks and measured appear that the theory does not envisage, then either the theory should be modified, or it is necessary to specify the limits of them.
• If the theory predicts effects, then it is necessary to seek to observe them and to measure them. For example, the predictive astrophysical theories confirm that there are laws or rules which govern the behavior of the Univers. As follows:
• laws of conservation (see Theorem of Noether),
• principles the maximum one and minima, like those of Maupertuis and Hamilton ?

Right

In the Right, the term of theory can have two objects. Either it indicates a solution with a problem of right proposed in general by the doctrines which release it from jurisprudence, even of the state of the substantive law. This theory proposes the application of a precise rule when a situation checks certain given criteria. The theory thus proposes a simple and rigorous framework which facilitates decision making in concrete cases. A theory can be invalidated by a reversal of jurisprudence or a contrary law. In this direction, the theories are simple statements and relate to very limited fields of the right. Legal examples of theories are, in Administrative law, the Théorie of the domanial changes and the Théorie of unforeseen subjections. Either it indicates what certain positivists, since the end of the 19th century and the beginning of 20th, tried to build, namely a speech about the right which tends to apprehend it in a total way, and to try to include/understand its intrinsic mechanisms (if as well is as there are some). The theorist, contrary to the doctor (within the meaning of that which takes part in the doctrines; to include/understand: those which emit an opinion within the legal community), following in that a tradition that they make go up in particular in Kant differentiating the judgment in fact and the value judgment, should not carry not value judgment on the right (he does not say if the right is well or badly, if he must remain such as he is or that he should be changed…), but only to describe it. This analysis in terms of speech or rather of language and meta-language (what is the theory of the right, right being the " language objet" , that about which one speaks) is due to Hans Kelsen, author in particular of the pure Théorie of the Right (1962, for the second edition, LGDJ-Bruylant, coll the Legal Thought). Its work is perpetuated in France in particular by Otto Pfesrmann (by ex: legal Reasoning and interpretation , under dir it. Pfersmann and Timsit, Publications of the Sorbonne, Paris 2001) and Michel Troper (by ex: Theory of the right, the right, the State , PUF, 2001) which worked out each one their own comprehension of Kelsen, and directed their work in this direction.

Examples of theories

• Theory of the numbers (in mathematics);

• Theory of the cords (in physics);
• Theory of chaos (in mechanics);
• Theory of the codes (in data processing);
• Theory of the red queen (in biology);
• Theory of demand, currency and interest rate (in economy);
• Theory of the languages (in linguistics).

See too

Simple: Theory