popper-logic-scientific-discovery

appendix *i 317
either lead to an infinite regress, or operate with an aprioristic principle
of induction, a synthetic principle which cannot be empirically tested.
If we distinguish, with Reichenbach, between a ‘procedure of finding’
and a ‘procedure of justifying’ a hypothesis, then we have to say
that the former—the procedure of finding a hypothesis—cannot be
rationally reconstructed. Yet the analysis of the procedure of justifying
hypotheses does not, in my opinion, lead us to anything which may be
said to belong to an inductive logic. For a theory of induction is
superfluous. It has no function in a logic of science.
Scientific theories can never be ‘justified’, or verified. But in spite of
this, a hypothesis A can under certain circumstances achieve more than
a hypothesis B—perhaps because B is contradicted by certain results of
observations, and therefore ‘falsified’ by them, whereas A is not falsified;
or perhaps because a greater number of predictions can be derived
with the help of A than with the help of B. The best we can say of a
hypothesis is that up to now it has been able to show its worth, and that
it has been more successful than other hypotheses although, in principle,
it can never be justified, verified, or even shown to be probable.
This appraisal of the hypothesis relies solely upon deductive consequences
(predictions) which may be drawn from the hypothesis.
There is no need even to mention induction.
The mistake usually made in this field can be explained historically:
science was considered to be a system of knowledge—of knowledge as
certain as it could be made. ‘Induction’ was supposed to guarantee the
truth of this knowledge. Later it became clear that absolutely certain
truth was not attainable. Thus one tried to get in its stead at least some
kind of watered-down certainty or turth; that is to say, ‘probability’.
But speaking of ‘probability’ instead of ‘truth’ does not help us to
escape either from the infinite regress or from apriorism. 1
From this point of view, one sees that it is useless and misleading to
employ the concept of probabiliy in connection with scientific
hypotheses.
The concept of probability is used in physics and in the theory of
games of chance in a definite way which may be satisfactorily defined
1 Cf. Popper, Logik der Forschung, for example pp. 188 and 195 f. *(of the original edition);
that is, sections 80 and 81.