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


In science, a theory is a mathematical or logical explanation, or 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 falsified 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 and 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 statement "It's not a fact, it's only a theory." True descriptions of reality are more reflectively understood as statements which would be true independently of what people think about them. In this usage, the word is synonymous with hypothesis.


In scientific usage, a theory does not mean an unsubstantiated guess or hunch, as it can in everyday speech. A theory is a logically self-consistent model or framework for describing the behavior of a related set of natural or social phenomena. It originates from or is supported by experimental evidence. In this sense, a theory is a systematic and formalized expression of all previous observations, and is predictive, logical, and testable. As such, scientific theories are essentially the equivalent of what everyday speech refers to as facts. In principle, scientific theories are always tentative, and subject to corrections or inclusion in a yet wider theory. Commonly, a large number of more specific hypotheses may be logically bound together by just one or two theories. As a general rule for use of the term, theories tend to deal with much broader sets of universals than do hypotheses, which ordinarily deal with much more specific sets of phenomena or specific applications of a theory.


The term theoretical is sometimes used to describe a result which 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 which are later confirmed or proven incorrect by experiment.


Theories are constructed in order to explain, predict and master phenomena (e.g. inanimate things, events, or the behavior of animals). In many instances we are constructing models of reality. A theory makes generalizations about observations and consists of an interrelated, coherent set of ideas and models.


According to Stephen Hawking in A Brief History of Time, "a theory is a good theory if it satisfies two requirements: It must accurately describe a large class of observations on the basis of a model which contains only a few arbitrary elements, and it must make definite predictions about the results of future observations". He goes on to state, "any physical theory is always provisional, in the sense that it is only a hypothesis; you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation which disagrees with the predictions of the 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."


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 which constrains how scientists theorize and model a phenomenon and thus arrive at testable hypotheses.


The defining characteristic of a scientific theory is that it makes falsifiable or testable predictions about things not yet observed. The relevance, and specificity of those predictions determine how (potentially) useful the theory is. A would-be theory which makes no predictions which can be observed is not a useful theory. Predictions which are 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. That is, it:


  • is consistent with pre-existing theory to the extent that the pre-existing theory was experimentally verified, though it will often show pre-existing theory to be wrong in an exact sense, and

  • is supported by many strands of evidence rather than a single foundation, ensuring that it is probably a good approximation, if not totally correct.


Additionally, a theory is generally only taken seriously if it:


  • is tentative, correctable and dynamic, in allowing for changes to be made as new data is discovered, rather than asserting certainty, and

  • 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.


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


  • It is easy to obtain confirmations, or verifications, for nearly every theory — if we look for confirmations.

  • 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.

  • Every "good" scientific theory is a prohibition: it forbids certain things to happen. The more a theory forbids, the better it is.

  • 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.

  • 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.

  • 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.")

  • 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 because, as Philip Kircher 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.” 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 that we view scientific theories as consisting of 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:


  • 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).

  • 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 raised more questions than it can currently answer. But incompleteness is now vice. On the contrary, incompleteness is the mother of fecundity …. A good theory should be productive; it should raise new questions and presume that those questions can be answered without giving up its problem-solving strategies” (1982: 47-48).

  • 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.


This article is licensed under the der the GNU Free Documentation License. It uses material from the Wikipedia article "Theory".




Popular IR Theorists

Popular Dictionary Terms

©2007 All Rights Reserved.  •  Design by FAMFAMFAM.