What is "theory"

Theory \The"o*ry\, n.; pl. Theories. [F. th['e]orie, L. theoria, Gr. ? a beholding, spectacle, contemplation, speculation, fr. ? a spectator, ? to see, view. See Theater.]

1. A doctrine, or scheme of things, which terminates in speculation or contemplation, without a view to practice; hypothesis; speculation.

   Note: ``This word is employed by English writers in a very loose and improper sense. It is with them usually convertible into hypothesis, and hypothesis is commonly used as another term for conjecture. The terms theory and theoretical are properly used in opposition to the terms practice and practical. In this sense, they were exclusively employed by the ancients; and in this sense, they are almost exclusively employed by the Continental philosophers.''
   --Sir W. Hamilton.

2. An exposition of the general or abstract principles of any science; as, the theory of music.

3. The science, as distinguished from the art; as, the theory and practice of medicine.

4. The philosophical explanation of phenomena, either physical or moral; as, Lavoisier's theory of combustion; Adam Smith's theory of moral sentiments.

   Atomic theory, Binary theory, etc. See under Atomic, Binary, etc.

   Syn: Hypothesis, speculation.

   Usage: Theory, Hypothesis. A theory is a scheme of the relations subsisting between the parts of a systematic whole; an hypothesis is a tentative conjecture respecting a cause of phenomena.

1590s, "conception, mental scheme," from Late Latin theoria (Jerome), from Greek theoria "contemplation, speculation; a looking at, viewing; a sight, show, spectacle, things looked at," from theorein "to consider, speculate, look at," from theoros "spectator," from thea "a view" (see theater) + horan "to see," possibly from PIE root *wer- (4) "to perceive" (see ward (n.)).\n

\nEarlier in this sense was theorical (n.), late 15c. Sense of "principles or methods of a science or art" (rather than its practice) is first recorded 1610s (as in music theory, which is the science of musical composition, apart from practice or performance). Sense of "an intelligible explanation based on observation and reasoning" is from 1630s.

n. 1 (context obsolete English) Mental conception; reflection, consideration. (16th-18th c.) 2 (context sciences English) A coherent statement or set of ideas that explains observed facts or phenomenon, or which sets out the laws and principles of something known or observed; a hypothesis confirmed by observation, experiment etc. (from 17th c.)

1. n. a well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena; "theories can incorporate facts and laws and tested hypotheses"; "true in fact and theory"

2. a tentative theory about the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena; "a scientific hypothesis that survives experimental testing becomes a scientific theory"; "he proposed a fresh theory of alkalis that later was accepted in chemical practices" [syn: hypothesis, possibility]

3. a belief that can guide behavior; "the architect has a theory that more is less"; "they killed him on the theory that dead men tell no tales"

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. The word has its roots in ancient Greek, but in modern use it has taken on several different related meanings.

A theory can be normative (or prescriptive), meaning a postulation about what ought to be. It provides "goals, norms, and standards". A theory can be a body of knowledge, which may or may not be associated with particular explanatory models. To theorize is to develop this body of knowledge.

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 characterized by the word 'hypothesis'). Scientific theories are distinguished from hypotheses, which are individual empirically testable conjectures, and scientific laws, which are descriptive accounts of how nature will behave under certain conditions.

In mathematical logic, a theory (also called a formal theory) is a set of sentences in a formal language. Usually a deductive system is understood from context. An element ϕ ∈ T of a theory T is then called an axiom of the theory, and any sentence that follows from the axioms (T ⊢ ϕ) is called a theorem of the theory. Every axiom is also a theorem. A first-order theory is a set of first-order sentences.

T heory (stylized as theory and known in Japan as ) is a New York-based men's and women's contemporary fashion label which sells clothes and accessories. The brand currently has 221 retail locations around the world, with global sales approaching $1 billion in 2014. The company’s headquarters and flagship boutique are located in Manhattan’s Meatpacking District.

"Theory" is a poem from Wallace Stevens's first book of poetry, Harmonium. It was first published in 1917, so it is in the public domain.

The instances are instances of imagination at work, as in the creation of a poem. They are not instances of a scientific theory, for they represent the particularizing quality of the imagination, not the generalizing that takes place in scientific reasoning. (This is itself a generalization from the theoretical or "scientific" perspective being minorized, which the line "Women understand this" also partakes of.) They may allude to a theory about poetry to the effect that it should be local, engaging the environment one has roots in. (See the main Harmonium essay about localism.) But the instances are so loosely connected to any particular locale that they suggest the theory's refutation (as unconvincing as the theory premised on locale is to begin with). The poet's imagination can go anywhere.

Buttel interprets the poem as one of Stevens's attempts to approach the rhythms of prose, as part of a strategic understatement that moves into a poem in an offhand, `anti-poetic' way. He sees that the instances must carry the strength of the theory, but he says nothing about how to understand theory in Stevens's specific sense, and nothing about what strength amounts to in this context.

Compare the opening line to Byron's assertion in the first lines of Canto III, Stanza LXXII of Childe Harold's Pilgrimage: "I live not in myself, but I become / Portion of that around me."

The word theory refers to a speculative explanation or to a confirmed explanation. In academic usage, the word theory refers to analytical tools for understanding, explaining, and making predictions in various fields of study:

• Mathematical theory, a self-consistent body of definitions, axioms, theorems, examples, and so on
• Theory (mathematical logic), a set of sentences (theorems) in a formal language
• Scientific theory, a principle or body of principles for explaining observed facts or phenomena, such as cell theory and the theory of gravity
• Philosophical theory, the collective statements underlying a philosophy, school of thought, or belief system
• Literary theory, often just called "theory" by those in the field
• Theories in computer science, such as computational complexity theory, computability theory, and theory of computation

Other uses:

• Theoria in theological discussions
• Theory (clothing retailer)
• A type of argument in Policy debate and Lincoln-Douglas debate