popper-logic-scientific-discovery

NOTE TO NEW APPENDICES,
1959 EDITION
Although I found, to my surprise, that I could still agree with almost all
the philosophical views expressed in the book, and even with most of
those on probability—a field in which my ideas have changed more
than in any other—I felt that I had to append to it some of the new
material accumulated through the years. There was a considerable
amount of this, for I never stopped working on the problems raised in
the book; and it was therefore not possible to include in these new
appendices all my relevant results. I must mention especially one result
that is missing here. It is the propensity interpretation of probability (as I call it).
The exposition and discussion of this interpretation grew, quite against
my intentions, until it became the main part of a new book.
The title of this new book is Postscript: After Twenty Years. It is a sequel to
the present book, and it contains much that is closely related to it, quite
apart from probability theory. In this connection I may also refer to two
papers of mine which I might have included among these appendices
had I not been reluctant to add to them any further. They are ‘Three
Views Concerning Human Knowledge’, and ‘Philosophy of Science: A
Personal Report’. 1
1 Published respectively in Contemporary British Philosophy 3, ed. by H. D. Lewis, 1956, pp.
355–388, and in British Philosophy in the Mid-Century, ed. by C. A. Mace, 1957, pp. 153–191.
Both are now in my Conjectures and Refutations, 1963, 1965 (chs. 1 and 3).