popper-logic-scientific-discovery

264
some structural components of a theory of experience
82 THE POSITIVE THEORY OF CORROBORATION: HOW
A HYPOTHESIS MAY ‘PROVE ITS METTLE’
Cannot the objections I have just been advancing against the probability
theory of induction be turned, perhaps, against my own view? It
might well seem that they can; for these objections are based on the
idea of an appraisal. And clearly, I have to use this idea too. I speak of the
‘corroboration’ of a theory; and corroboration can only be expressed as an
appraisal. (In this respect there is no difference between corroboration
and probability.) Moreover, I too hold that hypotheses cannot be
asserted to be ‘true’ statements, but that they are ‘provisional conjectures’
(or something of the sort); and this view, too, can only be
expressed by way of an appraisal of these hypotheses.
The second part of this objection can easily be answered. The
appraisal of hypotheses which indeed I am compelled to make use of,
and which describes them as ‘provisional conjectures’ (or something
of the sort) has the status of a tautology. Thus it does not give rise to
difficulties of the type to which inductive logic gives rise. For this
description only paraphrases or interprets the assertion (to which it is
equivalent by definition) that strictly universal statements, i.e. theories,
cannot be derived from singular statements.
The position is similar as regards the first part of the objection which
concerns appraisals stating that a theory is corroborated. The appraisal
of the corroboration is not a hypothesis, but can be derived if we are
given the theory as well as the accepted basic statements. It asserts the
fact that these basic statements do not contradict the theory, and it does
this with due regard to the degree of testability of the theory, and to
the severity of the tests to which the theory has been subjected, up to a
stated period of time.
We say that a theory is ‘corroborated’ so long as it stands up to these
tests. The appraisal which asserts corroboration (the corroborative
appraisal) establishes certain fundamental relations, viz. compatibility
and incompatibility. We regard incompatibility as falsification of the
theory. But compatibility alone must not make us attribute to the theory
a positive degree of corroboration: the mere fact that a theory has
not yet been falsified can obviously not be regarded as sufficient. For
nothing is easier than to construct any number of theoretical systems