Confirmation holism

Confirmation holism, also called epistemological holism is the claim that a single scientific theory cannot be tested in isolation; a test of one theory always depends on other theories and hypotheses.

That theories can only be tested as they relate to other theories implies that one can always claim that test results that seem to refute a favoured scientific theory have not refuted that theory at all. Rather, one can claim that the test results conflict with predictions because some other theory is false or unrecognised. Maybe the test equipment was out of alignment because the cleaning lady bumped into it the previous night. Or, maybe, there is dark matter in the universe that accounts for the strange motions of some galaxies.

That one cannot unambiguously determine which theory is refuted by unexpected data means that scientists must use judgments about which theories to accept and which to reject. Logic alone does not guide such decisions.

Duhem–Quine thesis

The Duhem–Quine thesis (also called the Duhem–Quine problem) 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). The hypothesis in question is by itself incapable of making predictions. Instead, the consequences of the hypothesis typically rest on background assumptions from which to derive predictions. This prevents a theory from becoming conclusively falsified through empirical means if the background assumptions are not proven (since background assumptions sometimes involve one or more scientific theories, and scientific theories are never strictly proven).

For instance, to "disprove" the idea that the Earth was moving, some people noted that birds did not get thrown off into the sky whenever they let go of a tree branch. That datum is no longer accepted as empirical evidence that the Earth is not moving because we have adopted a different background system of physics that allows us to make different predictions.

Another example. In the first half of the 19th century, astronomers were observing the path of the planet Uranus to see if it conformed to the path predicted by Newton's law of gravitation. It did not. There were an indeterminate number of possible explanations, such as that the telescopic observations were wrong because of some unknown factor; or that Newton's laws were in error; or some other factors affected observational data. However, it was eventually accepted that an unknown planet was affecting the path of Uranus, and that the hypothesis that there are seven planets in our solar system was rejected. Le Verrier calculated the approximate position of the interfering planet and its existence was confirmed in 1846. We now call the planet Neptune.

Although a bundle of theories (i.e. a theory and its background assumptions) as a whole can be tested against the empirical world and be falsified if it fails the test, the Duhem–Quine thesis says it is impossible to isolate a single hypothesis in the bundle. One solution to the dilemma thus facing scientists is that when we have rational reasons to accept the background assumptions as true (e.g. scientific theories via evidence) we will have rational—albeit nonconclusive—reasons for thinking that the theory tested is probably wrong if the empirical test fails.

While underdetermination does not invalidate the principle of falsifiability first presented by Karl Popper, Popper himself acknowledged that continual ad hoc modification of a theory provides a means for a theory to avoid being falsified (cf. Lakatos). In this respect, the principle of parsimony, or Occam's Razor, plays a role. This principle presupposes that between multiple theories explaining the same phenomenon, the simplest theory—in this case, the one that is least dependent on continual ad hoc modification—is to be preferred.

Pierre Duhem

As popular as the Duhem–Quine thesis may be in philosophy of science, in reality Pierre Duhem and Willard Van Orman Quine stated very different theses. Duhem believed that only in the field of physics can a single individual hypothesis not be isolated for testing. He says in no uncertain terms that experimental theory in physics is not the same as in fields like physiology and certain branches of chemistry. Also, Duhem's conception of "theoretical group" has its limits, since he states that not all concepts are connected to each other logically. He did not include at all a priori disciplines such as logic and mathematics within the theoretical groups in physics, since they cannot be tested experimentally.

Willard Van Orman Quine

Quine, on the other hand, in his "Two Dogmas of Empiricism", presents a much stronger version of underdetermination in science. His theoretical group embraces all of human knowledge, including mathematics and logic. He contemplated the entirety of human knowledge as being one unit of empirical significance. Hence all our knowledge, for Quine, would be epistemologically no different from ancient Greek gods, which were posited in order to account for experience. Quine even believed that logic and mathematics can also be revised in light of experience, and presented quantum logic as evidence for this. Years later he retracted this position; in his book Philosophy of Logic, he said that to revise logic would be essentially "changing the subject". In classic logic, connectives are defined according to truth values. The connectives in a multi-valued logic, however, have a different meaning than those of classic logic. As for quantum logic, it is not even a logic based on truth values, so the logical connectives lose the original meaning of classic logic. Quine also notes that deviant logics usually lack the simplicity of classic logic, and are not so fruitful.

Theory ladenness

Theory-laden　There are two aspects of confirmation holism. The first is that interpretation of observation is dependent on theory (sometimes called ). Before accepting the telescopic observations one must look into the optics of the telescope, the way the mount is constructed in order to ensure that the telescope is pointing in the right direction, and that light travels through space in a straight line (which itself is sometimes not so, as Einstein demonstrated). The second is that evidence alone is insufficient to determine which theory is correct. Each of the alternatives above might have been correct, but only one was in the end accepted.

Logical formulation

Theory-dependence of observations

Suppose some theory T implies an observation O (observation meaning here the result of the observation, rather than the process of observation per se):

$T\rightarrow O$

The required observation (result), however, is not found, i.e.

$\sim O$

So by Modus Tollens,

$\sim T$

All observations make use of prior assumptions, which can be symbolised as:

$O\equiv \left(p_{1}\wedge p_{2}\wedge p_{3}\cdots p_{n}\right)$

and therefore

$\sim O\equiv \sim \left(p_{1}\wedge p_{2}\wedge p_{3}\cdots \wedge p_{n}\right)$

which is by De Morgan's law equivalent to

$\sim \left(p_{1}\wedge p_{2}\wedge p_{3}\cdots \wedge p_{n}\right)\equiv \left(\sim p_{1}\vee \sim p_{2}\vee \sim p_{3}\cdots \vee \sim p_{n}\right)$.

In other words, the failure to make some observation only implies the failure of at least one of the prior assumptions that went into making the observation. It is always possible to reject an apparently falsifying observation by claiming that only one of its underlying assumptions is false; since there are an indeterminate number of such assumptions, any observation can potentially be made compatible with any theory. So it is quite valid to use a theory to reject an observation.

Underdetermination of a theory by evidence

Similarly, a theory consists of some indeterminate conjunction of hypotheses,

$T\equiv \left(h_{1}\wedge h_{2}\wedge h_{3}\cdots \wedge h_{n}\right)$

and so

$\sim T\equiv \sim \left(h_{1}\wedge h_{2}\wedge h_{3}\cdots \wedge h_{n}\right)$

which implies that

$\sim \left(h_{1}\wedge h_{2}\wedge h_{3}\cdots \wedge h_{n}\right)\equiv \left(\sim h_{1}\vee \sim h_{2}\vee \sim h_{3}\cdots \vee \sim h_{n}\right)$

In words, the failure of some theory implies the failure of at least one of its underlying hypotheses. It is always possible to resurrect a falsified theory by claiming that only one of its underlying hypotheses is false; again, since there are an indeterminate number of such hypotheses, any theory can potentially be made compatible with any particular observation. Therefore it is in principle impossible to determine if a theory is false by reference to evidence.

References

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• Curd, Martin; Cover, J.A. (Eds.) (1998). Philosophy of Science, Section 3, The Duhem-Quine Thesis and Underdetermination, W.W. Norton & Company.
• D. Davidson. 'On the Very Idea of Conceptual Scheme.' Proceedings of the American Philosophical Association, 17 (1973-74), pp. 5-20.
• Duhem, Pierre. The Aim and Structure of Physical Theory. Princeton, New Jersey, Princeton University Press, 1954.
• Gillies, Donald. "The Duhem Thesis and the Quine Thesis", in Martin Curd and J.A. Cover ed. Philosophy of Science: The Central Issues, (New York: Norton, 1998), 302-319. This paper is extract from Donald Gillies Philosophy of Science in the Twentieth Century (Oxford: Blackwell Publishers, 1993). The third chapter of the Philosophy of Science: The Central Issues also contains relevant excerpts from Duhem's work, The Aim and Structure of Physical Theory, and reprints Quine's "Two Dogmas of Empiricism" which are important works for Duhem and Quine's thought on this topic.
• W. V. Quine. 'Two Dogmas of Empiricism.' The Philosophical Review, 60 (1951), pp. 20-43. online text. Retrieved September 4, 2008.
• W. V. Quine. 'Ontological Relativity.' In Ontological Relativity and Other Essays, New York, Columbia University Press, 1969, pp. 26-68.
• W. V. Quine. Word and Object. Cambridge, Mass., MIT Press, 1960.

See also

• Truth
• Truth theory
• Coherentism
• Underdetermination

Theories of truth

Coherence theory of truth Consensus theory of truth Correspondence theory of truth Deflationary theory of truth

Epistemic theories of truth Pragmatic theory of truth Redundancy theory of truth Semantic theory of truth

Related topics

Belief Epistemology Information Inquiry

Knowledge Pragmatism Pragmaticism Pragmatic maxim

Reproducibility Scientific method Testability Verificationism

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