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Formulate different versions of the Duhem- Quine underdetermination thesis and

compare them.

In this essay I will focus on two versions of the Duhem-Quine

underdetermination thesis (DQUT), firstly on Duhem’s understanding

famously expressed in his article ‘Physical Theory and Experiment’, secondly

on Quine’s understanding spelled out in his article ‘Two Dogmas of

Empiricism’ and ‘On empirically equivalent systems of the world’ (Quine 1975,

2013). In doing so, I will compare both versions with respect to their

similarities, differences, and regarding their view on science, their

implications, and shortcomings; mainly with reference to Laudan (2013),

Gillies (2013), and Ariew (1984). In this essay I will present the argument

that what is called in the literature a weak version of the DQUT (associated

with Duhem) or a strong version of the DQUT (associated with Quine) is

not as different as presented by the above mentioned authors. The

difference between the weak and the strong version of

underdetermination is a difference in the weighting of each component

of the DQUT. The components of each thesis of underdetermination

are: a thesis about holism, here one can distinguish between a holist

understanding favoured by Duhem and one by Quine, which I will

argue, are not as different as they may appear; and a thesis about the

non-uniqueness of theories. The latter thesis is contributed by Quine.

Although an underdetermination thesis based solely on Quine or Duhem

can be obtained, this thesis would be in Laudan’s sense not of any

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philosophical interest. Thus only taken together a fuller thesis of

underdetermination can be spelled out.

Following Ariew’s (1984) understanding of Duhem, two claims can be

assigned to him: firstly the thesis of non-separability, what I have called

his thesis of holism, and secondly his thesis of the ambiguity of

falsification, which is a consequence of the former claim and lends

credence to Quine’s scepticism about conclusive verification. In

Duhem’s words his thesis of holism says that “an experiment in physic

can never condemn an isolated hypothesis but only a whole theoretical

group” (2013, 230). This is to say, that no theoretical statement (derived

from a theory) can be directly tested by observation. Only together with

further auxiliary hypothesis and assumptions any theoretical statement

can be tested by experience and observation. Duhem limits his claim to

physical theories only, which is according to Gillies and Ariew one of the

strengths of his thesis, however subsequently I will show that this

restriction is not plausible; furthermore I will reject Gillies’s distinction

between high- and low-level hypotheses. Duhem’s holism-thesis leads to

his rejection of crucial experiments, which supports his thesis about the

ambiguity of falsification. According to Duhem, a crucial experiment is one,

which on the one hand falsifies a rival theory and on the other hand

establishes its rival as confirmed. However, logic does not tell us whether

the scientist should reject his theory or any proposed auxiliary hypothesis

and furthermore in physics the refutation of one theory does not

establish with necessity its rival, since more than two theories (T and

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Not-T) are possible within physics. Thus, naïve falsificationism is not

applicable. Initially, it may seem reasonable to frame crucial experiments as

it was done by Duhem, although, his example of Foucault’s experiment

seems to have the power to decide between two rival theories and thus

seems to question Duhem’s strong denial of the possibility of any crucial

experiment; this decision-power of Foucault’s experiment was explained

by Duhem with his very underdeveloped notion of good sense. The good

sense of a physicist tells him when and whether he should abandon his

initial theory or should continue to adjust auxiliary hypothesis. This

notion of good sense seems to distinguish Duhem clearly from Quine,

for whom, any “statement can be held true come what may”(Quine

2013, 266). I will show in the next section, that this interpretation of

Quine by Ariew, Laudan, and Gillies is mistaken.

Quine is commonly associated with a strong version of the DQUT.

According to Gillies, Quine holds a comprehensive holism, which

includes the entire body knowledge, whereas Duhem restricts his holism

to physical theories. This is, although expressed by Duhem explicitly, a

wrong and untenable restriction of Duhem’s holism. As soon as auxiliary

hypotheses are involved, this is to say, as soon as any kind of

measurement instrument is involved, it cannot be said, in the case of

falsification, what exactly has been falsified. Duhem’s claim, that this

problem is relevant only in physics, is simply a bias due to his own

background as a physicist, because in any other scientific field measuring

instruments are used and have to be used. In short, his restriction is

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arbitrary and not defensible. His argumentation can be extended even to

observations in general where no measuring instrument was explicitly

used. Quine (1975), for example, argues that each observation, as soon as

it is relevant for science, becomes an observational statement, and hence

relies on a language, which is learned and thus is not infallible:

“Observation sentences are not incorrigible” (316). This means, that, in

the case of falsification, even when only direct observations are

concerned, it is not clear what has been falsified. This mistake leads to a

further problem within Gillies’ interpretation of Duhem, which I want to

discuss shortly. The distinction made by Gillies between low-level and

high-level hypothesis, where the former can be directly falsified by

observation and the latter only with the help of auxiliary hypothesis, is, in

the light of the discussion of observational statements, obsolete. Quine

(2013) argues, unaware of Duhem’s article (2013), against the distinction

between synthetic and analytic statements (dogma of analyticity) and against

the dogma of reductionism, which are eventually identical according to

Quine. As a consequence, Quine can argue that the whole body of

knowledge is at stake and nothing can be a priori excluded from any

adjustment and alteration. This is to say, that in the light of any

observational statement, and as long as the scientist is prepared to make

adjustments to the rest of the system (including logic and maths since

there is no analytic/synthetic distinction) anything could be confirmed

(266); this is also known as Quine’s non-uniqueness thesis. Prima facie,

the statement that the entire body of knowledge is at stake, makes

Quine’s DQUT appears very strong. This ‘strength’, however, can only

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be attributed to Quine’s thesis, if Quine, according to Laudan (2013),

also had implied a broader egalitarian thesis1 (292-3) and that this

egalitarian thesis was meant to be normative2. The first point is a logical

necessity and can without trouble be assigned to Quine, but the second

point about the normative intention, cannot be attributed to Quine,

without ignoring his explicit writings. Quine explicitly states in a letter to

Grünbaum that his thesis “as I [Quine] have used it is probably trivial”

(1976, 132) and furthermore in his later article he rejected any strong

interpretation of his under-determination thesis (1975). This

misinterpretation by Laudan is due to the fact that he did not take the

context of Quine’s argumentation seriously enough. In Quine’s article

(2013) the context of his notion of DQUT is the rejection of the ‘two

dogmas of empiricism’ and after this rejection, his prima facie strong notion of

underdetermination follows logically3. Another common

misunderstanding, which serves as an argument to reject Quine’s

DQUT, is how the entire body of the human knowledge is at stake,

when experience and observational statement, yield by a theory,

contradict each other (Ariew 1984). The profane question is just why, for

example, anything said in biology and in a theory from biology should

matter for an experience-observational statement inconsistency. There

are two understandings of the interrelatedness of scientific theory. Figure 1 „Every theory is as well supported by the evidence as any of its rivals“ (Laudan 2013, 292) 2 „It is rational to hold onto any theory whatever in the face of any evidence whatever“ (Laudan 2013, 293) 3 The implications of the not-normative meaning of Quine’s DQUT are outside of the scope of this essay.

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As already introduced Duhem proposes the good sense of a scientist in

order to know when to abandon a theory or merely adjust auxiliary

hypothesis. Quine’s solution is often overlooked and very opaque: “upon

our vaguely pragmatic inclination to adjust one strand of the fabric of

science rather than another in accommodating some particular

recalcitrant experience” (2013, 268). Thus, it is not completely arbitrary

which part and how much a scientist wants to alter assumptions and

theory in order to bring it in line with any given experience, this however

does not imply a normative claim. Following Stanford’s interpretation

(2013), Quine’s solution towards the underdetermination of any

scientific theory looks as follows: the “actual revisions of the web of

belief seek to maximize the theoretical “virtues” of simplicity, familiarity,

scope, and fecundity” or in Quine’s picture the “traditional distinction

between analytic and synthetic beliefs as simply registering the endpoints

of a psychological continuum ordering our beliefs according to the ease

and likelihood with which we are prepared to revise them in order to

reconcile the web as a whole with our sense experience”. This pragmatic

reasoning compared to Duhem’s good sense seems to be compatible, or

Quine’s pragmatism could be an account of Duhem’s good sense of a

scientist. In sum, also this feature of the DQUT does not seem to

distinguish Duhem’s and Quine’s notion of DQUT.

In a nutshell, I have argued, that neither the scope, the breadth nor the

imagined solution by Duhem’s and Quine’s notion of the DQUT are

sufficient to make a clear distinction between both notions possible,

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although this has been commonly argued in the literature. The only

difference, which remains, is the direction of the argumentation. Duhem

starts his reasoning from a particular theory and claims that in light of

new evidence the revision of this theory is underdetermined, whereas

Quine starts from a body of evidence and claims that more than one

theory would fit any given evidence logically. But the direction from

which underdetermination is spelled out does not lead to different

notions of underdetermination.

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Bibliography

Ariew, Roger. 1984. "The Duhem Thesis." The British Journal for the Philosophy of Science no. 35 (4):313-325. doi: 10.2307/687336.

Duhem, Pierre. 2013. "Physical Theory and Experiment." In Philosophy of science : the central issues, edited by Martin Curd, J. A. Cover and Christopher Pincock, 227-249. New York: W.W. Norton.

Gillies, Donald. 2013. "The Duhem Thesis and the Quine Thesis." In Philosophy of science : the central issues, edited by Martin Curd, J. A. Cover and Christopher Pincock, 271-287. New York: W.W. Norton.

Laudan, Larry. 2013. "Demystifying Underdetermination." In Philosophy of science : the central issues, edited by Martin Curd, J. A. Cover and Christopher Pincock, 288-320. New York: W.W. Norton.

Quine, Willard van Orman. 1975. "On empirically equivalent systems of the world." Erkenntnis no. 9 (3):313-328. doi: 10.1007/BF00178004.

Quine, Willard van Orman. 1976. "A comment on Grünbaum's claim." In Can theories be refuted? Essays on the Duhem-Quine thesis, edited by Sandra G. Harding, 132. Dordrecht.

Quine, Willard van Orman. 2013. "Two Dogmas of Empiricism." In Philosophy of science : the central issues, edited by Martin Curd, J. A. Cover and Christopher Pincock, 250-270. New York: W.W. Norton.

Stanford, Kyle. 2013. Underdetermination of Scientific Theory. In The Stanford Encyclopedia of Philosophy edited by Edward N. Zalta.