Theory: Difference between revisions

Template:Two other uses A theory in the most general terms is a set of statements (sometimes called the elementary theorems of the theory), each of which has been taken to be true, and which together support a particular conclusion which explains a given set of facts. Theories are tools used in different fields of knowledge. They are formed using the methodology of those various fields and within the context of the subject matter being studied. Theories are constructed so as to describe a unifying principle that explains a body of facts and the laws based on them. In other words, it is an explanation to a set of observations.

Whereas a

tentative, and intellectually honest fashion as opposed to being regarded as having been conclusively established. This practice is so as to account for the possibility that the theory was arrived at using potentially faulty inferences or observations. In these cases the term theory does not suggest a low confidence in the claim and many uses of the term in the sciences require just the opposite. In cases where a counterexample is produced that appears to falsify a theory, in fact we can only conclude, at most, that at least one of the theorems of the theory is invalid (but cannot necessarily say which one.)

Etymology

The word is derived from Greek θεωρία

Scientific theories

In the sciences generally, theories are constructed from elementary theorems that consist in empirical data about observable phenomena. A scientific theory is used as a plausible general principle or body of principles offered to explain a phenomenon.^[3]

A major concern in construction of scientific theories is the problem of demarcation, i.e., distinguishing those ideas that are properly studied by the sciences and those that are not.

Philosophical theories

Theories whose subject matter consists not in empirical data, but rather in ideas are in the realm of philosophical theories as contrasted with scientific theories. At least some of the elementary theorems of a philosophical theory are statements whose truth cannot necessarily be scientifically tested through empirical observation.

Theories are intended to be an accurate, predictive description of the natural world. However, it is sometimes not clear whether the conclusions derived from the theory inform us about the nature of the world, or the nature of the theory.

Pedagogical definition

Finally, in pedagogical contexts or in official pronouncements by official organizations of scientists one gets a definition like the following.

According to the

,

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 supported by facts gathered over time. Theories also allow scientists to make predictions about as yet unobserved phenomena, ^[4]

A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment. Such fact-supported theories are not "guesses" but reliable accounts of the real world. The theory of biological evolution is more than "just a theory." It is as factual an explanation of the universe as the atomic theory of matter or the germ theory of disease. Our understanding of gravity is still a work in progress. But the phenomenon of gravity, like evolution, is an accepted fact.^[5]

The primary advantage enjoyed by this definition is that it firmly marks things termed theories as being well supported by evidence. This would be a disadvantage in interpreting real discourse between scientists who often use the word theory to describe untested but intricate hypotheses in addition to repeatedly confirmed models. However, in an educational or mass media setting it is almost certain that everything of the form X theory is an extremely well supported and well tested theory. This causes the theory/non-theory distinction to much more closely follow the distinctions useful for consumers of science (e.g. should I believe something or not?)

The term theoretical

The term theoretical is sometimes informally used in lieu of hypothetical to describe a result that is predicted by theory but has not yet been adequately tested by observation or experiment. It is not uncommon for a theory to produce predictions that are later confirmed or proven incorrect by experiment. By inference, a prediction proved incorrect by experiment demonstrates the hypothesis is invalid. This either means the theory is incorrect, or the experimental conjecture was wrong and the theory did not predict the hypothesis.

In physics

In

. Note that the specific theoretical aspects of classical electromagnetic theory, which have been consistently and successfully replicated for well over a century, are termed "laws of electromagnetism", reflecting that they are today taken for granted. Within electromagnetic theory generally, there are numerous hypotheses about how electromagnetism applies to specific situations. Many of these hypotheses are already considered to be adequately tested, with new ones always in the making and perhaps untested.

Theories as "models"

Purpose

Theories are constructed to explain, predict, and master phenomena (e.g., inanimate things, events, or behavior of animals). In many instances we are constructing

. A theory makes generalizations about observations and consists of an interrelated, coherent set of ideas and models.

Description and prediction

Echoing the philosopher Karl Popper,

inductive logic

.

Assumptions to formulate a theory

This is a view shared by Isaac Asimov. In Understanding Physics, Asimov spoke of theories as "arguments" where one deduces a "scheme" or model. Arguments or theories always begin with some premises—"arbitrary elements" as Hawking calls them (see above)—which are here described as "assumptions". An assumption according to Asimov is...

...something accepted without proof, and it is incorrect to speak of an assumption as either true or false, since there is no way of proving it to be either (If there were, it would no longer be an assumption). It is better to consider assumptions as either useful or useless, depending on whether deductions made from them corresponded to reality. ... On the other hand, it seems obvious that assumptions are the weak points in any argument, as they have to be accepted on faith in a philosophy of science that prides itself on its rationalism. Since we must start somewhere, we must have assumptions, but at least let us have as few assumptions as possible.

(See

)

Example: Special Theory of Relativity

As an example of the use of assumptions to formulate a theory, consider how

). He assumed both observations to be correct, and formulated his theory, based on these assumptions, by simply altering the Galilean transformation to accommodate the lack of addition of velocities with regard to the speed of light. The model created in his theory is, therefore, based on the assumption that light maintains a constant velocity (or more commonly: the speed of light is a constant).

Example: Ptolemy

An example of how theories are models can be seen from theories on the planetary system. The Greeks formulated theories, which the astronomer

. So one can see that a theory is a "model of reality" that explains certain scientific facts; yet the theory may not be a satisfactory picture of reality. Another, more acceptable, theory can later replace the previous model, as when the Copernican theory replaced the Ptolemaic theory. Or a new theory can be used to modify an older theory as when Einstein modified Newtonian mechanics (which is still used for computing planetary orbits or modeling spacecraft trajectories) with his theories of relativity.

Differences between theory and model

Central to the nature of models, from general models to scale models, is the employment of representation (literally, "re-presentation") to describe particular aspects of a phenomenon or the manner of interaction among a set of phenomena. For instance, a scale model of a house or of a solar system is clearly not an actual house or an actual solar system; the aspects of an actual house or an actual solar system represented in a scale model are, only in certain limited ways, representative of the actual entity. In most ways that matter, the scale model of a house is not a house. Several commentators (e.g., Reese & Overton 1970; Lerner, 1998; Lerner & Teti, 2005, in the context of modeling human behavior) have stated that the important difference between theories and models is that the first is explanatory as well as descriptive, while the second is only descriptive (although still predictive in a more limited sense). General models and theories, according to philosopher Stephen Pepper (1948)—who also distinguishes between theories and models—are predicated on a "root" metaphor that constrains how scientists theorize and model a phenomenon and thus arrive at testable hypotheses.

Engineering practice makes a distinction between "mathematical models" and "physical models."

Characteristics

In a famous comment on a paper someone showed him, Wolfgang Pauli captured the difference between scientific and unscientific thought by saying, "This isn't right. It's not even wrong."

Essential criteria

The defining characteristic of a scientific theory is that it makes

. The relevance and specificity of those predictions determine how potentially useful the theory is. A would-be theory that makes no predictions that can be observed is not a useful theory. Predictions not sufficiently specific to be tested are similarly not useful. In both cases, the term "theory" is inapplicable.

In practice a body of descriptions of knowledge is usually only called a theory once it has a minimum empirical basis, according to certain criteria:

• It is consistent with pre-existing theory, to the extent the pre-existing theory was experimentally verified, though it will often show pre-existing theory to be wrong in an exact sense.
• It is supported by many strands of evidence, rather than a single foundation, ensuring it is probably a good approximation, if not totally correct.

Non-essential criteria

Additionally, a theory is generally only taken seriously if:

• It is tentative, correctable, and dynamic in allowing for changes as new facts are discovered, rather than asserting certainty.
• It is the most parsimonious explanation, sparing in proposed entities or explanations—commonly referred to as passing the Occam's razor test.

This is true of such established theories as special and general relativity, quantum mechanics, plate tectonics, evolution, etc. Theories considered scientific meet at least most, but ideally all, of these extra criteria.

Theories do not have to be perfectly accurate to be scientifically useful. The predictions made by Classical mechanics are known to be inaccurate, but they are sufficiently good approximations in most circumstances that they are still very useful and widely used in place of more accurate but mathematically difficult theories.

Indistinguishable theories

Sometimes two theories make exactly the same predictions. A pair of such theories is called indistinguishable, and the choice between them reduces to convenience or philosophical preference.

Criterion for scientific status

Karl Popper described the characteristics of a scientific theory as follows:

1. It is easy to obtain confirmations, or verifications, for nearly every theory—if we look for confirmations.
2. Confirmations should count only if they are the result of risky predictions; that is to say, if, unenlightened by the theory in question, we should have expected an event which was incompatible with the theory—an event which would have refuted the theory.
3. Every "good" scientific theory is a prohibition: it forbids certain things to happen. The more a theory forbids, the better it is.
4. A theory which is not refutable by any conceivable event is non-scientific. Irrefutability is not a virtue of a theory (as people often think) but a vice.
5. Every genuine test of a theory is an attempt to falsify it, or to refute it. Testability is falsifiability; but there are degrees of testability: some theories are more testable, more exposed to refutation, than others; they take, as it were, greater risks.
6. Confirming evidence should not count except when it is the result of a genuine test of the theory; and this means that it can be presented as a serious but unsuccessful attempt to falsify the theory. (I now speak in such cases of "corroborating evidence".)
7. Some genuinely testable theories, when found to be false, are still upheld by their admirers—for example by introducing ad hoc some auxiliary assumption, or by reinterpreting the theory ad hoc in such a way that it escapes refutation. Such a procedure is always possible, but it rescues the theory from refutation only at the price of destroying, or at least lowering, its scientific status. (I later describe such a rescuing operation as a "conventionalist twist" or a "conventionalist stratagem".)

One can sum up all this by saying that according to Popper, the criterion of the scientific status of a theory is its falsifiability, or refutability, or testability.

Several philosophers and historians of science have, however, argued that Popper's definition of theory as a set of falsifiable statements is wrong ^[6] because, as Philip Kitcher has pointed out, if one took a strictly Popperian view of "theory", observations of Uranus when first discovered in 1781 would have "falsified" Newton's celestial mechanics. Rather, people suggested that another planet influenced Uranus' orbit—and this prediction was indeed eventually confirmed.

Kitcher agrees with Popper that "There is surely something right in the idea that a science can succeed only if it can fail." ^[7] He also takes into account Hempel and Quine's critiques of Popper, to the effect that scientific theories include statements that cannot be falsified (presumably what Hawking alluded to as arbitrary elements), and the point that good theories must also be creative. He insists we view scientific theories as an "elaborate collection of statements", some of which are not falsifiable, while others—those he calls "auxiliary hypotheses", are.

According to Kitcher, good scientific theories must have three features:

1. Unity: "A science should be unified…. Good theories consist of just one problem-solving strategy, or a small family of problem-solving strategies, that can be applied to a wide range of problems" (1982: 47).
2. Fecundity: "A great scientific theory, like Newton's, opens up new areas of research…. Because a theory presents a new way of looking at the world, it can lead us to ask new questions, and so to embark on new and fruitful lines of inquiry…. Typically, a flourishing science is incomplete. At any time, it raises more questions than it can currently answer. But incompleteness is not vice. On the contrary, incompleteness is the mother of fecundity…. A good theory should be productive; it should raise new questions and presume those questions can be answered without giving up its problem-solving strategies" (1982: 47–48).
3. Auxiliary hypotheses that are independently testable: "An auxiliary hypothesis ought to be testable independently of the particular problem it is introduced to solve, independently of the theory it is designed to save" (1982: 46) (e.g. the evidence for the existence of Neptune is independent of the anomalies in Uranus's orbit).

Like other definitions of theories, including Popper's, Kitcher makes it clear that a good theory includes statements that have (in his terms) "observational consequences". But, like the observation of irregularities in the orbit of Uranus, falsification is only one possible consequence of observation. The production of new hypotheses is another possible—and equally important—observational consequence.

Mathematics

In

.

The term

(concepts of randomness and likelihood).

statements about them. As a result, some domains of knowledge cannot be formalized, accurately and completely, as mathematical theories. (Here, formalizing accurately and completely means that all true propositions—and only true propositions—are derivable within the mathematical system.) This limitation, however, in no way precludes the construction of mathematical theories that formalize large bodies of scientific knowledge.

Other fields

Theories exist not only in the so-called hard sciences, but in all fields of academic study, from philosophy to music to literature.

In the humanities, theory is often used as an abbreviation for critical theory or literary theory.

List of notable theories

• Astronomy: Big Bang Theory
• Biology: Cell theory — Evolution
• Atomic theory — Kinetic theory of gases
• Theory of Global Climate Change
  (due to anthropogenic activity)
• Computer science: Algorithmic information theory — Computation theory
• Economics: Decision theory
• Progressive education theory
• Signal theory — Systems theory
• Film: Film Theory
• Games: Combinatorial game theory — Game theory — Rational choice theory
• Geology: Plate tectonics
• Humanities: Critical theory
• Literature: Literary theory
• Mathematics: Catastrophe theory — Category theory — Chaos theory — Graph theory — Knot theory — Number theory — Probability theory — Set theory
• Music: Music theory
• Virtue theory
• Antenna theory — BCS theory — Landau theory — Theory of relativity — Quantum field theory
• Giant impact theory
• Art Educational theory — Architecture — Composition — Anatomy — Color theory — Perspective — Visual perception — Geometry — Manifolds
• Critical theory
• Statistics : Extreme value theory
• Theatre : Theory relating to theatrical performance.
• Other:
  Obsolete scientific theories — Phlogiston theory

Scientific laws

Main article: Scientific law

Scientific laws are similar to scientific theories in that they are principles that can be used to predict the behavior of the natural world. Both scientific laws and scientific theories are typically well-supported by observations and/or experimental evidence. Usually scientific laws refer to rules for how nature will behave under certain conditions.^[8] Scientific theories are more overarching explanations of how nature works and why it exhibits certain characteristics.

A common misconception is that scientific theories are rudimentary ideas that will eventually graduate into scientific laws when enough data and evidence has been accumulated. A theory does not change into a scientific law with the accumulation of new or better evidence. A theory will always remain a theory, a law will always remain a law. ^[9]

See also

• List of theories
• Falsifiability
• Formal language
• Formal system
• Hypothesis
• Hypothesis testing
• Model
• Predictive power
• Scientific method
• Testability

Notes

1. ^ Frisk; derivation from θεός was suggested by Koller Glotta 36, 273ff.
2. ^ Harper, Douglas. "theory". Online Etymology Dictionary. Retrieved 2008-07-18.
3. ^ Merriam-Webster.com Merriam-Webster Dictionary: Theory in Science
4. National Academy of Sciences (2005), Science, Evolution, and Creationism, a brochure on the book of the same title
   .
5. ^ AAAS Evolution Resources
6. ^ Hempel. C.G. 1951 "Problems and Changes in the Empiricist Criterion of Meaning" in Aspects of Scientific Explanation. Glencoe: the Free Press. Quine, W.V.O 1952 "Two Dogmas of Empiricism" reprinted in From a Logical Point of View. Cambridge: Harvard University Press
7. ^ Philip Kitcher 1982 Abusing Science: The Case Against Creationism. Page 45 Cambridge: The MIT Press
8. Physical law
   , for example.
9. ^ theory

References

• Popper, Karl (1963), Conjectures and Refutations, Routledge and Kegan Paul, London, UK, pp. 33–39. Reprinted in Theodore Schick (ed., 2000), Readings in the Philosophy of Science, Mayfield Publishing Company, Mountain View, Calif., pp. 9–13.
• Chairman of Biology and Kennesaw State Ronald Matson's webpage comparing scientific laws and theories
• Hawking, Stephen (1996). "The Illustrated A Brief History of Time" (Updated and expanded ed.). New York: Bantam Books, p. 15.
• Mohr, Johnathon (2008). "Revelations and Implications of the Failure of Pragmatism: The Hijacking of Knowledge Creation by the Ivory Tower". New York: Ballantine Books. pp. 87–192.