Goodman’s riddle was an insurmountable obstacle to the positivist project of describing
the logic of confirmation in purely syntactic terms.
Further problems with the Received View arose in the area of explanation. Its account
of scientific explanation is the ‘deductive-nomological model’ (DNM), which claims that
explanation occurs through the explanandum of a scientific explanation––a statement
describing what is explained––being deductively implied by other true statements, that
describe laws of nature and initial conditions.25 This met with a number of difficulties,26
the most well known one being the case of the flagpole. From laws about the behaviour of
light and information about the height of a flagpole and its location relative to the sun, we
can deduce––and thus explain––the length of the flagpole’s shadow. However, we can
equally well deduce the height of the flagpole from the length of its shadow. We want to
say that the height explains the length of the shadow, not vice versa, but the DNM provides
no resources for doing this.
The Received View’s account of theoretical terms was a strict working out of Locke’s
claim that nominal definitions were the only ones useful in science. The severe problems
encountered by this account called into question this Lockean approach. One line of
objection came from scientific realists, who wanted to understand statements about theoretical,
unobservable entities such as atoms as true claims about the existence of
unobservable entitites, rather than assertions whose meaning was exhausted by their
implications for observable happenings. Another line of objection called into question the
demarcation between theoretical and observational terms. With the abandonment of the
Empiricist ‘way of ideas’, and its modern descendant, phenomenalism, and the replacement
of statements about sensation in the object language of positivist theories with
statements about physical objects and happenings, it became harder to draw a principled
distinction between these categories.27
A further objection came from Quine, inspired by Duhem. He pointed out that assertions
about theoretical entities cannot in fact be translated into claims about a specific subgroup
of observational statements, and then confirmed or falsified according as these statements
turn out to be true or false, and asserted that ‘our statements about the external world face
the tribunal of sense experience not individually but only as a corporate body’. (Quine
1961, p. 41.) An example to illustrate this claim can be taken from astronomy; basing a
scientific judgment on what we see through a telescope requires us to assume laws of optics
as governing the telescope’s image, and is thus not simply an appeal to our visual
experience.