# The Logic of Scientific Discovery

By Karl R. Popper | Go to book overview

CHAPTER X
CORROBORATION, OR HOW A THEORY STANDS UP TO TESTS

THEORIES are not verifiable, but they can be 'corroborated'.

The attempt has often been made to describe theories as being neither true nor false, but instead more or less probable. Inductive logic, more especially, has been developed as a logic which may ascribe not only the two values 'true' and 'false' to statements, but also degrees of probability; a type of logic which will here be called 'probability logic'. According to those who believe in probability logic, induction should determine the degree of probability of a statement. And a principle of induction should either make it sure that the induced statement is 'probably valid' or else it should make it probable, in its turn--for the principle of induction might itself be only 'probably valid'. Yet in my view, the whole problem of the probability of hypotheses is misconceived. Instead of discussing the 'probability' of a hypothesis we should try to assess what tests, what trials, it has withstood; that is, we should try to assess how far it has been able to prove its fitness to survive by standing up to tests. In brief, we should try to assess how far it has been 'corroborated'.*1

____________________
*1
I introduced the terms 'corroboration' ('Bewæhrung') and especially 'degree of corroboration' ('Grad der Bewæhrung', 'Bewæhrungsgrad') in my book because I wanted a neutral term to describe the degree to which a hypothesis has stood up to severe tests, and thus 'proved its mettle'. By 'neutral' I mean a term not prejudging the issue whether, by standing up to tests, the hypothesis becomes 'more probable', in the sense of the probability calculus. In other words, I introduced the term 'degree of corroboration' mainly in order to be able to discuss the problem whether or not degree of corroboration' could be indentified with 'probability' (either in a frequency sense or in the sense of Keynes, for example).

Carnap translated my term 'degree of corroboration' ('Grad der Bewæhrung'), which I had first introduced into the discussions of the Vienna Circle, as 'degree of confirmation'. (See his "'Testability and Meaning'", in Philosophy of Science 3, 1936; especially p. 427); and so the term 'degree of confirmation' soon became widely accepted. I did not like this term, because of some of its associations ('make firm'; 'establish firmly';

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