Theory is a contemplative and rational type of abstract or generalizing thinking, or the results of such thinking. Depending on the context, the results might for example include generalized explanations of how nature works, or even how divine or metaphysical matters are thought to work. The word has its roots in ancient Greek, but in modern use it has taken on several different related meanings.

One modern group of meanings emphasizes the speculative and generalizing nature of theory. For example in the arts and philosophy, the term "theoretical" may be used to describe ideas and empirical phenomena which are not easily measurable. And by extension of the philosophical meaning, "theoria" is also a word still used in theological contexts. As already in Aristotle's definitions, theory is very often contrasted to "practice" (from Greek praxis, πρᾶξις) a Greek term for "doing", which is opposed to theory because pure theory involves no doing apart from itself. A classical example of the distinction between theoretical and practical uses the discipline of medicine: medical theory involves trying to understand the causes and nature of health and sickness, while the practical side of medicine is trying to make people healthy. These two things are related but can be independent, because it is possible to research health and sickness without curing specific patients, and it is possible to cure a patient without knowing how the cure worked.

In modern science, the term "theory" refers to scientific theories, a well-confirmed type of explanation of nature, made in a way consistent with scientific method, and fulfilling the criteria required by modern science. Such theories are described in such a way that any scientist in the field is in a position to understand and either provide empirical support ("verify") or empirically contradict ("falsify") it. Scientific theories are the most reliable, rigorous, and comprehensive form of scientific knowledge, in contrast to more common uses of the word "theory" that imply that something is unproven or speculative (which is better defined by the word 'hypothesis'). Scientific theories are also distinguished from hypotheses, which are individual empirically testable conjectures, and scientific laws, which are descriptive accounts of how nature will behave under certain conditions.

Read more about Theory:  Ancient Uses, Theories Formally and Scientifically, Philosophical Theories, Scientific Theories, List of Notable Theories

Other articles related to "theory":

Feudalism - Etymology
... The most widely held theory is put forth by Marc Bloch ... This Germanic origin theory was also shared by William Stubbs in the nineteenth century ... Another theory was put forward by Archibald R ...
Zermelo Set Theory
... Zermelo set theory, as set out in an important paper in 1908 by Ernst Zermelo, is the ancestor of modern set theory ...
J. Philippe Rushton - Work and Opinions - Application of r/K Selection Theory To Race
... book Race, Evolution, and Behavior (1995) uses r/K selection theory to explain how East Asians consistently average high, blacks low, and whites in the middle on an evolutionary scale of ... He first published this theory in 1984 ... He theorizes that r/K selection theory explains these differences ...
Falsifiability - The Criterion of Demarcation
... It is useful to know if a statement or theory is falsifiable, if for no other reason than that it provides us with an understanding of the ways in which one might assess the theory ... be saved from attempting to falsify a non-falsifiable theory, or come to see an unfalsifiable theory as unsupportable ... Popper claimed that, if a theory is falsifiable, then it is scientific ...
... minmax) is a decision rule used in decision theory, game theory, statistics and philosophy for minimizing the possible loss for a worst case (maximum loss ... Originally formulated for two-player zero-sum game theory, covering both the cases where players take alternate moves and those where they make ...

Famous quotes containing the word theory:

    The theory [before the twentieth century] ... was that all the jobs in the world belonged by right to men, and that only men were by nature entitled to wages. If a woman earned money, outside domestic service, it was because some misfortune had deprived her of masculine protection.
    Rheta Childe Dorr (1866–1948)

    It is not enough for theory to describe and analyse, it must itself be an event in the universe it describes. In order to do this theory must partake of and become the acceleration of this logic. It must tear itself from all referents and take pride only in the future. Theory must operate on time at the cost of a deliberate distortion of present reality.
    Jean Baudrillard (b. 1929)

    If my theory of relativity is proven correct, Germany will claim me as a German and France will declare that I am a citizen of the world. Should my theory prove untrue, France will say that I am a German and Germany will declare that I am a Jew.
    Albert Einstein (1879–1955)