popper-logic-scientific-discovery

experience; a point with which I agree. He believes that he must therefore
choose the ‘simplest’ theory. But since the conventionalist does
not treat his theories as falsifiable systems but rather as conventional
stipulations, he obviously means by ‘simplicity’ something different
from degree of falsifiability.
The conventionalist concept of simplicity turns out to be indeed
partly aesthetic and partly practical. Thus the following comment by
Schlick (cf. section 42) applies to the conventionalist concept of simplicity,
but not to mine: ‘It is certain that one can only define the
concept of simplicity by a convention which must always be arbitrary.’
1 It is curious that conventionalists themselves have overlooked
the conventional character of their own fundamental concept—that of
simplicity. That they must have overlooked it is clear, for otherwise they
would have noticed that their appeal to simplicity could never save
them from arbitrariness, once they had chosen the way of arbitrary
convention.
From my point of view, a system must be described as complex in the
highest degree if, in accordance with conventionalist practice, one holds
fast to it as a system established forever which one is determined to
rescue, whenever it is in danger, by the introduction of auxiliary
hypotheses. For the degree of falsifiability of a system thus protected is
equal to zero. Thus we are led back, by our concept of simplicity, to the
methodological rules of section 20; and especially also to that rule or
principle which restrains us from indulgence in ad hoc hypotheses and
auxiliary hypotheses: to the principle of parsimony in the use of
hypotheses.
Addendum, 1972
In this chapter I have tried to show how far degrees of simplicity can be
identified with degrees of testability. Nothing depends on the word
‘simplicity’: I never quarrel about words, and I did not seek to reveal
the essence of simplicity. What I attempted was merely this:
Some great scientists and philosophers have made assertions about
simplicity and its value for science. I suggested that some of these
1 Schlick, ibid., p. 148.
simplicity 131