Three criticisms of conventional views about the relation between theory and evidence from the Duhem selection:
Holism. (Duhem, section 2, pp.
230-34; see also the application to Newtonian celestial mechanics, p. 239. Laudan calls this "the ambiguity of
falsification" on p. 293.) This is the idea that evidence does not bear directly on a
hypothesis alone, but rather on a hypothesis in conjunction with many additional
theoretical claims (as well as assumptions about particular facts, e.g. about the
Let H be the hypothesis we wish to test; let A1, A2, and A3 be the additional theoretical and particular assumptions needed to deductively imply an observation statement, and let O be the observation statement.
Then we may think of Duhem as making the following point. If H, together with A1, A2, and A3, implies O, then the following conditional will be true:
(H & A1 & A2 & A3) → O
From this, together with ~O, we can deduce, not ~H, but only
~(H & A1 & A2 & A3)
Which (by DeMorgan's laws) is equivalent to
~H ∨ ~A1 ∨ ~A2 ∨ ~A3
--that is, we can conclude only that at least one of the hypothesis or our starting assumptions is false. Observation and logic will not tell us which one is false.
Laudan thinks all of these points (well, really he only addresses 1 and 4) are correct and to some extent important, but that they do not have significant relativistic consequences. These points concern deductive underdetermination. Relativists have concluded that, since logic doesn't compel one theory choice over another, there must be a significant nonrational component in theory choice.
But Laudan points out that to show this would require not merely deductive underdetermination, but ampliative underdetermination. (An "ampliative inference" is one which goes beyond what you could infer by means of deduction alone: for instance, an inference from the evidence to claims about the future, or the distant past, or things too small or far away to observe directly. If we use the term "induction" broadly enough, an ampliative inference is just an inductive inference.) That is, what needs to be shown is not that observation plus deduction will not determine theory choice, but rather that "ampliative inference" will not determine a unique choice of theory. Laudan argues that no one has in fact shown this.
On the other hand, Laudan doesn't say much about what ampliative principles might cure underdetermination. It seems clear that deductive reasoning alone will not narrow the range of acceptable theories to one. Goodman's puzzle suggests that deductive reasoning plus enumerative induction (aka the straight rule of induction, or the instantial model of induction) still leaves significant underdetermination. What can fill the gap? That is, what principles can we use to narrow down the choices between theories that are still left standing by deduction and enumerative induction?
Proposed criteria have included: simplicity, fruitfulness, generality, etc. (Duhem himself proposes "good sense" at the end of his article, though this unfortunately seems somewhat vague!)
If all rational criteria still underdetermine theory choice, then it seems that something else will need to fill the gap. This is where defenders of an extreme sociological account of science have seen an opportunity: if reason doesn't determine which theories to accept, then it will need to be supplemented by social or psychological factors: individual bias, political commitments, and the like.
Curd, Martin, J. A. Cover, and Christopher Pincock. 2013. Philosophy of Science: The Central Issues, Second Edition. Norton.
Duhem, Pierre. "Physical Theory and Experiment." In Curd et al., pp. 227-49. [Selections from Duhem, The Aim and Structure of Physical Theory, first published in French in 1906.]
Laudan, Larry. "Demystifying Underdetermination." In Curd et al., pp. 288-320. [First published 1990.]
"Some Assembly Required." Buffy the Vampire Slayer -- The Chosen Collection. Season Two, Episode Two. Written by Ty King, directed by Bruce Seth Green, Warner Brothers, 2006. [First broadcast 1997.]