Concept

Theory

Overview

A theory is, in general, a set of propositions or ideas about something, developed in a variety of ways through any sort of reasoning. This includes informal folk psychological theories of why someone behaves the way they do, scientific theories that attempt to explain some phenomenon, philosophical theories (for example of politics or the nature of reality), and a range of other uses. Not all theories are equal and they may, for example, by compared in terms of how well they explain a phenomenon and the strength of evidence for and against them.

When applied to intellectual or academic situations, it is considered a systematic and rational form of abstract thinking about a phenomenon, or the conclusions derived from such thinking. It involves contemplative and logical reasoning, often supported by processes such as observation, experimentation, and research. Theories can be scientific, falling within the realm of empirical and testable knowledge, or they may belong to non-scientific disciplines, such as art or philosophy. In some cases, theories may exist independently of any formal discipline.

In modern science, the term "theory" refers to scientific theories, a well-confirmed type of explanation of nature, made in a way consistent with the scientific method, and fulfilling the criteria required by modern science. Such theories are described in such a way that scientific tests should be able to provide empirical support for it, or empirical contradiction ("falsify") of 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 in formal terms is better characterized by the word hypothesis). Scientific theories are distinguished from hypotheses, which are individual empirically testable conjectures, and from scientific laws, which are descriptive accounts of the way nature behaves under certain conditions.

Theories guide the enterprise of finding facts rather than of reaching goals, and are neutral concerning alternatives among values. 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.

The word theory or "in theory" is sometimes used outside of science to refer to something which the speaker did not experience or test before. In science, this same concept is referred to as a hypothesis, and the word "hypothetically" is used both inside and outside of science. In its usage outside of science, the word "theory" is very often contrasted to "practice" (from Greek praxis, πρᾶξις) a Greek term for doing, which is opposed to theory. 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.

Overview adapted from Wikipedia (CC BY-SA 4.0; see the article history for authors).

In the original texts

Passages from public-domain books where Theory is discussed.

The view which any logician adopts as to the nature of the knowledge-process is accordingly conditioned by his metaphysical presuppositions as to the nature of reality. It is equally true that the theory of the judgment developed from any metaphysical standpoint serves as a test of the validity of that standpoint. We shall attempt in the present paper to show how Bosanquet's theory of the judgment develops from his…
John Dewey, Studies in Logical Theory
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In this, the proper sense of the word, Theory is the explanation of practice. In another and a more vulgar sense, theory means any mere fiction of the imagination, endeavoring to conceive how a thing may possibly have been produced, instead of examining how it was produced. In this sense only are theory and theorists unsafe guides; but because of this, ridicule or discredit is attempted to be attached to theory in…
John Stuart Mill, A System of Logic, Ratiocinative and Inductive
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A classification of types of theory is rendered difficult, a thoroughly satisfactory classification almost impossible, by the fact that the problems arrange themselves about separate principles leading to cross-divisions. All that we may expect to do is somewhat arbitrarily to select that principle which seems most likely to be useful in conducting inquiry.
John Dewey, Ethics
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We must therefore spend a little time in giving a bare outline, which is the less to be regretted as the theory is in itself fascinating.
Bertrand Russell, Philosophy
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But, further, if the theory is true, as we are supposing it to be, any other mode in which he tries, or in which he was formerly accustomed, to represent the phenomena, will be seen by him to be inconsistent with the facts that suggested the new theory--facts which now form a part of his mental picture of nature. And since a contradiction is always inconceivable, his imagination rejects these false theories, and…
John Stuart Mill, A System of Logic
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Theory

Overview

In the original texts

Philosophers who discussed Theory

Related ideas

Opposing perspectives

Place in the tradition