popper-logic-scientific-discovery

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new appendices
who identify, explicitly or implicitly, degree of corroboration, or of
confirmation, or of acceptability, with probability; the philosophers I
had in mind were especially Keynes, Jeffreys, Reichenbach, Kaila,
Hosiasson and, more recently, Carnap.
As to Carnap, I wrote a critical footnote which, I believe, speaks for
itself. It was motivated by the fact that Carnap, in stating adequacy
criteria for degree of confirmation, speaks of the consensus of ‘practically
all modern theories of degree of confirmation’, but does not mention
my dissent, in spite of the fact that he introduced the English term
‘degree of confirmation’ as a translation of my term ‘Grad der Bewährung’.
(Cf. the footnote before section 79, above.) Moreover, I wished to point
out that his division of probability into probability 1 (= his degree of
confirmation) and probability 2 (= statistical frequency) was insufficient:
that there were at the very least two interpretations of the calculus
of probability (the logical and the statistical) and that, in addition,
there was my degree of corroboration which was not a probability (as has
now been shown here, and as was shown in my note).
It seems that this ten-line footnote of mine has drawn more attention
to itself than the rest of my note. It led to a discussion in the B.J.P.S. 5
in which Bar-Hillel asserted that my criticism of what he termed ‘the
current theory of confirmation’ (i.e. Carnap’s theory) was purely verbal
and that all I had to say was anticipated by Carnap; and it led to a review
of my paper in the Journal of Symbolic Logic 6 in which Kemeny summed up
my note by the words: ‘The principal thesis of this paper is that
Carnap’s proposed measurers of degree of confirmation, or any other
assignment of logical probability, are not suited to measure degrees of
confirmation.’
This was certainly not my principal thesis. My note was a continuation
of some work of mine published fifteen years before Carnap’s
book was written; and as far as criticism is concerned, the point at
issue—the identification of corroboration or confirmation or acceptability
with probability—though it is of course the main thesis of
Carnap’s book, is far from being an original thesis of Carnap’s; for he is
5 See B.J.P.S. 6, 1955, pp. 155 to 163; and 7, 1956, pp. 243 to 256.
6 See J.S.L. 20, 1955, p. 304. The following is an error of fact in Kemeny’s review: in line
16 from the bottom of the page, ‘measure of support given by y to x’ should read
‘measure of the explanatory power of x with respect to y’.