What is the proper difinition of theory?

Question

What is the proper difinition of theory?

Answer 1

The American Heritage dictionary defines it thusly:

1. A set of statements or principles devised to explain a group of facts or phenomena, especially one that has been repeatedly tested or is widely accepted and can be used to make predictions about natural phenomena. 2. The branch of a science or art consisting of its explanatory statements, accepted principles, and methods of analysis, as opposed to practice: a fine musician who had never studied theory. 3. A set of theorems that constitute a systematic view of a branch of mathematics. 4. Abstract reasoning; speculation: a decision based on experience rather than theory. 5. A belief or principle that guides action or assists comprehension or judgment: staked out the house on the theory that criminals usually return to the scene of the crime. 6. An assumption based on limited information or knowledge; a conjecture.

(Note that many unscientifically trained people will cling to the definition #6, in a context where #1 is actually the appropriate meaning -- like for the theory of evolution, of gravity, of relativity)

According to the National Academy of Science:

Some scientific explanations are so well established that no new evidence is likely to alter them. The explanation becomes a scientific theory. In everyday language a theory means a hunch or speculation. Not so in science. In science, the word theory refers to a comprehensive explanation of an important feature of nature that is supported by many facts gathered over time. Theories also allow scientists to make predictions about as yet unobserved phenomena.

This is as good as it gets.

Answer 2

The word theory has a lot of distinct meanings in different fields of knowledge, depending on their methodologies and the context of discussion.

In science a theory is a testable model of the manner of interaction of a set of natural phenomena, capable of predicting future occurrences or observations of the same kind, and capable of being tested through experiment or otherwise verified through empirical observation. It follows from this that for scientists "theory" and "fact" do not necessarily stand in opposition. For example, it is a fact that an apple dropped on earth has been observed to fall towards the center of the planet, and the theories commonly used to describe and explain this behavior are Newton's theory of universal gravitation (see also gravitation), and the theory of general relativity.

In common usage, the word theory is often used to signify a conjecture, an opinion, or a speculation. In this usage, a theory is not necessarily based on facts; in other words, it is not required to be consistent with true descriptions of reality. This usage of theory leads to the common incorrect statements. True descriptions of reality are more reflectively understood as statements which would be true independently of what people think about them.

According to the National Academy of Sciences,

Some scientific explanations are so well established that no new evidence is likely to alter them. The explanation becomes a scientific theory. In everyday language a theory means a hunch or speculation. Not so in science. In science, the word theory refers to a comprehensive explanation of an important feature of nature that is supported by many facts gathered over time. Theories also allow scientists to make predictions about as yet unobserved phenomena.[1]

Answer 3

Theory (also related to theorem) stems from Greek 'to look at.'  The theory of music (objective and subjective) may differ from scientific theory (objective alone?).  A theory assembles observations and tries to explain (or guess) what they mean.  Many theories are very well established such as Newton's theory of gravity, but are then superseded for other conditions such as Einstein's theory of relativity necessary near the speed of light (which still holds Newton's theory true as a limiting, low velocity condition).  Theories may be pure speculation or well established and repeatable in independent labs.  Because instruments are not perfect it is even possible to produce theories that arise from the study of phenomena exhibiting effects hardly more significant than instrument error, where the investigator 'imagines' success.