popper-logic-scientific-discovery

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some structural components of a theory of experience
misconceived notion of a synthetic statement which is a priori valid, i.e.
an irrefutable statement about reality.
Thus if we try to turn our metaphysical faith in the uniformity of
nature and in the verifiability of theories into a theory of knowledge
based on inductive logic, we are left only with the choice between an
infinite regress and apriorism.
80 THE PROBABILITY OF A HYPOTHESIS AND
THE PROBABILITY OF EVENTS: CRITICISM OF
PROBABILITY LOGIC
Even if it is admitted that theories are never finally verified, may we not
succeed in making them secure to a greater or lesser extent—more
probable, or less so? After all, it might be possible that the question of
the probability of a hypothesis could be reduced, say, to that of the probability of
events, and thus be made susceptible to mathematical and logical
handling.* 1
Like inductive logic in general, the theory of the probability of
hypotheses seems to have arisen through a confusion of psychological
with logical questions. Admittedly, our subjective feelings of conviction
are of different intensities, and the degree of confidence with
which we await the fulfilment of a prediction and the further corroboration
of a hypothesis is likely to depend, among other things, upon
the way in which this hypothesis has stood up to tests so far—upon its
past corroboration. But that these psychological questions do not
belong to epistemology or methodology is pretty well acknowledged
even by the believers in probability logic. They argue, however, that it
is possible, on the basis of inductivist decisions, to ascribe degrees of
probability to the hypotheses themselves; and further, that it is possible to
reduce this concept to that of the probability of events.
The probability of a hypothesis is mostly regarded as merely a special
case of the general problem of the probability of a statement; and this in
* 1 The present section (80) contains mainly a criticism of Reichenbach’s attempt to
interpret the probability of hypotheses in terms of a frequency theory of the probability of events. A
criticism of Keynes’s approach is contained in section 83. *Note that Reichenbach is
anxious to reduce the probability of a statement or hypothesis (what Carnap many years later
called ‘probability 1 ’) to a frequency (‘probability 2 ’).