In the philosophy of science, underdetermination is the idea that evidence available to us at given time may be insufficient to determine what beliefs we should hold in response to it. [1] Underdetermination says that all evidence necessarily underdetermines any scientific theory [2]

Underdetermination exists when available evidence is insufficient to identify which belief one should hold about that evidence. For example, if all that was known was that exactly $10 was spent on apples and oranges, and that apples cost $1 and oranges $2, then one would know enough to eliminate some possibilities (e.g., 6 oranges could not have been purchased), but one would not have enough evidence to know which specific combination of apples and oranges was purchased. In this example, one would say that belief in what combination was purchased is underdetermined by the available evidence.


Ancient Greek skeptics argued for equipollence, the view that reasons for and against claims are equally balanced. This captures at least one sense of saying that the claims themselves are underdetermined.

Underdetermination, again under different labels, arises in the modern period in the work of René Descartes. Among other skeptical arguments, Descartes presents two arguments involving underdetermination. His dream argument points out that experiences perceived while dreaming (for example, falling) do not necessarily contain sufficient information to deduce the true situation (being in bed). He concluded that since one cannot always distinguish dreams from reality, one cannot rule out the possibility that one is dreaming rather than having veridical experiences; thus the conclusion that one is having a veridical experience is underdetermined. His demon argument posits that all of one's experiences and thoughts might be manipulated by a very powerful and deceptive "evil demon". Once again, so long as the perceived reality appears internally consistent to the limits of one's limited ability to tell, the situation is indistinguishable from reality and one cannot logically determine that such a demon does not exist.

Underdetermination and evidence

To show that a conclusion is underdetermined, one must show that there is a rival conclusion that is equally well supported by the standards of evidence. A trivial example of underdetermination is the addition of the statement "whenever we look for evidence" (or more generally, any statement which cannot be falsified). For example, the conclusion "objects near earth fall toward it when dropped" might be opposed by "objects near earth fall toward it when dropped but only when one checks to see that they do." Since one may append this to any conclusion, all conclusions are at least trivially underdetermined. If one considers such statements to be illegitimate, e.g. by applying Occam's Razor, then such "tricks" are not considered demonstrations of underdetermination.

This concept also applies to scientific theories: for example, it is similarly trivial to find situations that a theory does not address. For example, classical mechanics did not distinguish between non-accelerating reference frames. As a result, any conclusion about such a reference frame was underdetermined; it was equally consistent with the theory to say that the solar system is at rest, as it is to say that it moves at any constant velocity in any particular direction. Newton himself stated that these possibilities were indistinguishable. More generally, evidence may not always be sufficient to distinguish between competing theories (or to determine a different theory that will unify both), as is the case with general relativity and quantum mechanics.

Another example is provided by Goethe's Theory of Colours — "Newton believed that with the help of his prism experiments, he could prove that sunlight was composed of variously coloured rays of light. Goethe showed that this step from observation to theory is more problematic than Newton wanted to admit. By insisting that the step to theory is not forced upon us by the phenomena, Goethe revealed our own free, creative contribution to theory construction. And Goethe's insight is surprisingly significant, because he correctly claimed that all of the results of Newton's prism experiments fit a theoretical alternative equally well. If this is correct, then by suggesting an alternative to a well-established physical theory, Goethe developed the problem of underdetermination a century before Duhem and Quine's famous arguments." (Mueller, 2016)[3] Hermann von Helmholtz says of this — 'And I for one do not know how anyone, regardless of what his views about colours are, can deny that the theory in itself is fully consequent, that its assumptions, once granted, explain the facts treated completely and indeed simply'. (Helmholtz 1853)[4]

Arguments involving underdetermination

Arguments involving underdetermination attempt to show that there is no reason to believe some conclusion because it is underdetermined by the evidence. Then, if the evidence available at a particular time can be equally well explained by at least one other hypothesis, there is no reason to believe it rather than the equally supported rival (although many other hypotheses may still be eliminated).

Because arguments involving underdetermination involve both a claim about what the evidence is and that such evidence underdetermines a conclusion, it is often useful to separate these two claims within the underdetermination argument as follows:

  1. All the available evidence of a certain type underdetermines which of several rival conclusions is correct.
  2. Only evidence of that type is relevant to believing one of these conclusions.
  3. Therefore, there is no evidence for believing one among the rival conclusions.

The first premise makes the claim that a theory is underdetermined. The second says that rational decision (i.e. using available evidence) depends upon insufficient evidence.

Epistemological problem of the indeterminacy of data to theory

Any phenomenon can be explained by a multiplicity of hypotheses. How, then, can data ever be sufficient to prove a theory? This is the "epistemological problem of the indeterminacy of data to theory".

The poverty of the stimulus argument and W.V.O. Quine's 1960 'Gavagai' example are perhaps the most commented variants of the epistemological problem of the indeterminacy of data to theory.

General skeptical arguments

Some skeptical arguments appeal to the fact that no possible evidence could be incompatible with 'skeptical hypotheses' like the maintenance of a complex illusion by Descartes' evil demon or (in a modern version) the machines who run the Matrix. A skeptic may argue that this undermines any claims to knowledge, or even (by internalist definitions), justification.

Philosophers have found this argument very powerful. Hume felt it was unanswerable, but observed that it was in practice impossible to accept its conclusions. Influenced by this, Kant held that while the nature of the 'noumenal' world was indeed unknowable, we could aspire to knowledge of the 'phenomenal' world. A similar response has been advocated by modern anti-realists.

Underdetermined ideas are not implied to be incorrect (taking into account present evidence); rather, we cannot know if they are correct.

Philosophy of science

In the philosophy of science, underdetermination is often presented as a problem for scientific realism, which holds that we have reason to believe in entities that are not directly observable (such as electrons) talked about by scientific theories. One such argument proceeds as follows:

  1. All the available observational evidence for such entities underdetermines the claims of a scientific theory about such entities.
  2. Only the observational evidence is relevant to believing a scientific theory.
  3. Therefore, there is no evidence for believing what scientific theories say about such entities.

Particular responses to this argument attack both the first and the second premise (1 and 2). It is argued against the first premise that the underdetermination must be strong and/or inductive. It is argued against the second premise that there is evidence for a theory's truth besides observations; for example, it is argued that simplicity, explanatory power or some other feature of a theory is evidence for it over its rivals.

A more general response from the scientific realist is to argue that underdetermination is no special problem for science, because, as indicated earlier in this article, all knowledge that is directly or indirectly supported by evidence suffers from it—for example, conjectures concerning unobserved observables. It is therefore too powerful an argument to have any significance in the philosophy of science, since it does not cast doubt uniquely on conjectured unobservables.

See also

Notes and references

  1. ^ https://plato.stanford.edu/entries/scientific-underdetermination/. Missing or empty |title= (help)
  2. ^ (PDF) https://www.pitt.edu/~jdnorton/teaching/1702_jnrsnr_sem/1702_jnrsnr_seminar_2005/docs/underdet_thesis.pdf. Missing or empty |title= (help)
  3. ^ Mueller, Olaf L. (2016). "Prismatic Equivalence – A New Case of Underdetermination: Goethe vs. Newton on the Prism Experiments, 2016/2 (n° 24)". British Journal for the History of Philosophy. 24 (2): 323–347. doi:10.1080/09608788.2015.1132671.
  4. ^ Helmholtz, Hermann von. 1853. Goethes Vorahnungen kommender naturwissenschaftlicher Ideen. Berlin: Pastel. 1971. Philosophische Vortrdge und Aufsdtze. Ed. H. Horz and S. Wollgast. Berlin: Akademie-Verlag.

External links

Blind signal separation

Blind signal separation (BSS), also known as blind source separation, is the separation of a set of source signals from a set of mixed signals, without the aid of information (or with very little information) about the source signals or the mixing process. This problem is in general highly underdetermined, but useful solutions can be derived under a surprising variety of conditions. Much of the early literature in this field focuses on the separation of temporal signals such as audio. However, blind signal separation is now routinely performed on multidimensional data, such as images and tensors, which may involve no time dimension whatsoever.

Confirmation holism

In philosophy of science, confirmation holism, also called epistemological holism, is the view that no individual statement can be confirmed or disconfirmed by an empirical test, but only a set of statements (a whole theory).

It is attributed to Willard Van Orman Quine who motivated his holism through extending Pierre Duhem's problem of underdetermination in physical theory to all knowledge claims. Duhem's idea was, roughly, that no theory of any type can be tested in isolation but only when embedded in a background of other hypotheses, e.g. hypotheses about initial conditions. Quine thought that this background involved not only such hypotheses but also our whole web-of-belief, which, among other things, includes our mathematical and logical theories and our scientific theories. This last claim is sometimes known as the Duhem–Quine thesis. A related claim made by Quine, though contested by some (see Adolf Grünbaum 1962), is that one can always protect one's theory against refutation by attributing failure to some other part of our web-of-belief. In his own words, "Any statement can be held true come what may, if we make drastic enough adjustments elsewhere in the system."

Duhem–Quine thesis

The Duhem–Quine thesis, also called the Duhem–Quine problem, after Pierre Duhem and Willard Van Orman Quine, is that it is impossible to test a scientific hypothesis in isolation, because an empirical test of the hypothesis requires one or more background assumptions (also called auxiliary assumptions or auxiliary hypotheses). In recent decades the set of associated assumptions supporting a thesis sometimes is called a bundle of hypotheses.


Equifinality is the principle that in open systems a given end state can be reached by many potential means. Also meaning that a goal can be reached by many ways. The term and concept is due to Hans Driesch, the developmental biologist, later applied by Ludwig von Bertalanffy, the founder of general systems theory, and by William T. Powers, the founder of perceptual control theory. Driesch and von Bertalanffy prefer this term, in contrast to "goal", in describing complex systems' similar or convergent behavior. Powers simply emphasised the flexibility of response, since it emphasizes that the same end state may be achieved via many different paths or trajectories.

In closed systems, a direct cause-and-effect relationship exists between the initial condition and the final state of the system: When a computer's 'on' switch is pushed, the system powers up. Open systems (such as biological and social systems), however, operate quite differently. The idea of equifinality suggests that similar results may be achieved with different initial conditions and in many different ways. This phenomenon has also been referred to as isotelesis (from Greek ἴσος isos "equal" and τέλεσις telesis: "the intelligent direction of effort toward the achievement of an end") when in games involving superrationality.


Broadly speaking, fallibilism (from Medieval Latin: fallibilis, "liable to err") is the philosophical claim that no belief can have justification which guarantees the truth of the belief. However, not all fallibilists believe that fallibilism extends to all domains of knowledge.

Hypothetico-deductive model

The hypothetico-deductive model or method is a proposed description of scientific method. According to it, scientific inquiry proceeds by formulating a hypothesis in a form that can be falsifiable, using a test on observable data where the outcome is not yet known. A test outcome that could have and does run contrary to predictions of the hypothesis is taken as a falsification of the hypothesis. A test outcome that could have, but does not run contrary to the hypothesis corroborates the theory. It is then proposed to compare the explanatory value of competing hypotheses by testing how stringently they are corroborated by their predictions.


Indeterminacy or underdeterminacy may refer to:

Indeterminacy in computation (disambiguation)

Aleatoric music and indeterminacy in music.

Statically indeterminate

Indeterminacy (literature) a literary term

In set theory and game theory, the opposite of determinacy

In biology, indeterminate growth of an organism

Underdetermined system

Indeterminate systemIn law:

Indeterminacy debate in legal theory

Underdeterminacy (law)In linguistics:

Indeterminacy of translation

Referential indeterminacyIn philosophy:

Indeterminacy (philosophy)

Indeterminism, the belief that not all events are causally determined

Deterministic system (philosophy)

Philosophy of science Indeterminacy of theory under empirical testing.

UnderdeterminationIn physics:

Quantum indeterminacy

Uncertainty principle

Scientific determinism

Indeterminacy of translation

The indeterminacy of translation is a thesis propounded by 20th-century American analytic philosopher W. V. Quine. The classic statement of this thesis can be found in his 1960 book Word and Object, which gathered together and refined much of Quine's previous work on subjects other than formal logic and set theory. The indeterminacy of translation is also discussed at length in his Ontological Relativity. Crispin Wright suggests that this "has been among the most widely discussed and controversial theses in modern analytical philosophy". This view is endorsed by Putnam who states that it is "the most fascinating and the most discussed philosophical argument since Kant's Transcendental Deduction of the Categories".Three aspects of indeterminacy arise, of which two relate to indeterminacy of translation. The three indeterminacies are (i) inscrutability of reference, and (ii) holophrastic indeterminacy, and (iii) the underdetermination of scientific theory. The last of these, not discussed here, refers to Quine's assessment that evidence alone does not dictate the choice of a scientific theory. The first refers to indeterminacy in interpreting individual words or sub-sentences. The second refers to indeterminacy in entire sentences or more extensive portions of discourse.

Jan Westerhoff

Jan Christoph Westerhoff is a philosopher and orientalist with specific interests in metaphysics and the philosophy of language. He is currently Professor of Buddhist Philosophy in the Faculty of Theology and Religion of the University of Oxford.

Katarzyna Jaszczolt

Katarzyna M. (Kasia) Jaszczolt, D.Phil. (Oxon), Ph.D (Cantab), MAE () (b. 9 December 1963) is a Polish and British linguist and philosopher. She is currently Professor of Linguistics and Philosophy of Language at the University of Cambridge, and Professorial Fellow at Newnham College, Cambridge.She is the author of a theory of discourse interpretation, Default Semantics. This theory breaks away from the tradition of modelling utterance meaning by means of a sentence-based proposition and proposes instead so-called 'merger representations' – conceptual representations which combine the output of various linguistic and non-linguistic sources of information leading to the recovery of speaker meaning, shifting compositionality from the level of syntactic structures to the level of the merger.She has published widely on various topics in philosophy of language, semantics and pragmatics, including representing time in language and mind, ambiguity and underdetermination of meaning, propositional attitudes, and representing the self.

Observational equivalence

Observational equivalence is the property of two or more underlying entities being indistinguishable on the basis of their observable implications. Thus, for example, two scientific theories are observationally equivalent if all of their empirically testable predictions are identical, in which case empirical evidence cannot be used to distinguish which is closer to being correct; indeed, it may be that they are actually two different perspectives on one underlying theory.

In econometrics, two parameter values (or two structures, from among a class of statistical models) are considered observationally equivalent if they both result in the same probability distribution of observable data. This term often arises in relation to the identification problem.

In the formal semantics of programming languages, two terms M and N are observationally equivalent if and only if, in all contexts C[...] where C[M] is a valid term, it is the case that C[N] is also a valid term with the same value. Thus it is not possible, within the system, to distinguish between the two terms. This definition can be made precise only with respect to a particular calculus, one that comes with its own specific definitions of term, context, and the value of a term.


Overdetermination occurs when a single-observed effect is determined by multiple causes, any one of which alone would be sufficient to account for ("determine") the effect. That is, there are more causes present than are necessary to cause the effect. In the philosophy of science, this means that more evidence is available than is necessary to justify a conclusion. Overdetermination is in contrast to underdetermination, when the number or strength of causes is insufficient.

The term "overdetermination" (German: Überdeterminierung) was also used by Sigmund Freud as a key concept in his psychoanalysis.

Pig Latin

Pig Latin is a language game or argot in which words in English are altered, usually by adding a fabricated suffix or by moving the onset or initial consonant or consonant cluster of a word to the end of the word and adding a vocalic syllable to create such a suffix. For example, "Wikipedia" would become "Ikipediaway" (the "W" is removed from the beginning and has "ay" appended to create a suffix). The objective is to conceal the words from others not familiar with the rules. The reference to Latin is a deliberate misnomer; Pig Latin is simply a form of argot or jargon unrelated to Latin, and the name is used for its English connotations as a strange and foreign-sounding language. It is most often used by young children as a fun way to confuse people unfamiliar with Pig Latin.

Scientific realism

Scientific realism is the view that the universe described by science is real regardless of how it may be interpreted.

Within philosophy of science, this view is often an answer to the question "how is the success of science to be explained?" The discussion on the success of science in this context centers primarily on the status of unobservable entities apparently talked about by scientific theories. Generally, those who are scientific realists assert that one can make valid claims about unobservables (viz., that they have the same ontological status) as observables, as opposed to instrumentalism.

Strong programme

The strong programme or strong sociology is a variety of the sociology of scientific knowledge (SSK) particularly associated with David Bloor, Barry Barnes, Harry Collins, Donald A. MacKenzie, and John Henry. The strong programme's influence on Science and Technology Studies is credited as being unparalleled (Latour 1999). The largely Edinburgh-based school of thought has illustrated how the existence of a scientific community, bound together by allegiance to a shared paradigm, is a prerequisite for normal scientific activity.

The strong programme is a reaction against "weak" sociologies of science, which restricted the application of sociology to "failed" or "false" theories, such as phrenology. Failed theories would be explained by citing the researchers' biases, such as covert political or economic interests. Sociology would be only marginally relevant to successful theories, which succeeded because they had revealed a true fact of nature. The strong programme proposed that both "true" and "false" scientific theories should be treated the same way. Both are caused by social factors or conditions, such as cultural context and self-interest. All human knowledge, as something that exists in the human cognition, must contain some social components in its formation process.

The Imperial Physician

"The Imperial Physician" (Chinese: 太医; pinyin: Tàiyī) is a short story by the Chinese writer Pu Songling collected in Strange Tales from a Chinese Studio in 1740, and translated by Sidney L. Sondergard in 2012.


A 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 related meanings.

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.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 scientific tests should be able to provide empirical support for, 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 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.


Verisimilitude (or truthlikeness) is a philosophical concept that distinguishes between the relative and apparent (or seemingly so) truth and falsity of assertions and hypotheses. The problem of verisimilitude is the problem of articulating what it takes for one false theory to be closer to the truth than another false theory.This problem was central to the philosophy of Karl Popper, largely because Popper was among the first to affirm that truth is the aim of scientific inquiry while acknowledging that most of the greatest scientific theories in the history of science are, strictly speaking, false. If this long string of purportedly false theories is to constitute progress with respect to the goal of truth, then it must be at least possible for one false theory to be closer to the truth than others.

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