popper-logic-scientific-discovery

APPENDIX *ix
Corroboration, the Weight of
Evidence, and Statistical Tests
The three notes reprinted below in the present appendix were originally
published in The British Journal for the Philosophy of Science. 1
Even before my book was published, I felt that the problem of
degree of corroboration was one of those problems which should be
further investigated. By ‘the problem of degree of corroboration’ I
mean the problem (i) of showing that there exists a measure (to be
called degree of corroboration) of the severity of tests to which a theory
has been subjected, and of the manner in which it has passed these
tests, or failed them; and (ii) of showing that this measure cannot be a
probability, or more precisely, that it does not satisfy the formal laws of
the probability calculus.
An outline of the solution of both of these tasks—especially the
second—was contained in my book. But I felt that a little more was
needed. It was not quite enough to show the failure of the existing
theories of probability—of Keynes and of Jeffreys, for example, or of
Kaila, or of Reichenbach, none of whom could establish even their
central doctrine: that a universal law, or a theory, could ever reach a
1 B.J.P.S. 5, 1954, pp. 143 ff. (see also corrections on pp. 334 and 359); 7, 1957,
pp. 350 ff., and 8, 1958, pp. 294 ff.