popper-logic-scientific-discovery

78 INDETERMINIST METAPHYSICS
some observations on quantum theory 243
It is the task of the natural scientist to search for laws which will enable
him to deduce predictions. This task may be divided into two parts. On
the one hand, he must try to discover such laws as will enable him to
deduce single predictions (‘causal’ or ‘deterministic’ laws or ‘precision
statements’). On the other hand, he must try to advance hypotheses
about frequencies, that is, laws asserting probabilities, in order to deduce
frequency predictions. There is nothing in these two tasks to make them
in any way mutually incompatible. It is clearly not the case that whenever
we make precision statements we shall make no frequency hypotheses;
for some precision statements are, as we have seen, macro laws which
are derivable from frequency assumptions. Nor is it the case that whenever
in a particular field frequency statements are well confirmed, we
are entitled to conclude that in this field no precision statements can be
made. This situation seems plain enough. Yet the second of the two
conclusions we have just rejected has been drawn again and again. Again
and again we meet with the belief that where fortuity rules, regularity
is ruled out. I have critically examined this belief in section 69.
The dualism of macro and micro laws—I mean the fact that we
operate with both—will not be easily overcome, to judge by the present
state of scientific development. What might be logically possible,
however, is a reduction of all known precision statements—by interpreting
them as macro laws—to frequency statements. The converse
reduction is not possible. Frequency statements can never be deduced
from precision statements, as we have seen in section 70. They need
their own assumptions which must be specifically statistical. Only from
probability estimates can probabilities be calculated.* 1
This is the logical situation. It encourages neither a deterministic nor
an indeterministic view. And should it ever become possible to work in
physics with nothing but frequency statements, then we should still
not be entitled to draw indeterminist conclusions; which is to say that
we should still not be entitled to assert that ‘there are no precise laws
in nature, no laws from which predictions about the course of single
or elementary processes can be deduced’. The scientist will never let
* 1 This view is opposed by Einstein at the end of his letter here printed in appendix *xii.
But I still think that it is true.