popper-logic-scientific-discovery

7
SIMPLICITY
There seems to be little agreement as to the importance of the so-called
‘problem of simplicity’. Weyl said, not long ago, that ‘the problem of
simplicity is of central importance for the epistemology of the natural
sciences’. 1 Yet it seems that interest in the problem has lately declined;
perhaps because, especially after Weyl’s penetrating analysis, there
seemed to be so little chance of solving it.
Until quite recently the idea of simplicity has been used uncritically,
as though it were quite obvious what simplicity is, and why it should
be valuable. Not a few philosophers of science have given the concept
of simplicity a place of crucial importance in their theories, without
even noticing the difficulties to which it gives rise. For example, the
followers of Mach, Kirchhoff, and Avenarius have tried to replace the
idea of a causal explanation by that of the ‘simplest description’. Without
the adjective ‘simplest’ or a similar word this doctrine would say
nothing. As it is supposed to explain why we prefer a description of the
world with the help of theories to one with the help of singular statements,
it seems to presuppose that theories are simpler than singular
statements. Yet few have ever attempted to explain why they should be
simpler, or what is meant, more precisely, by simplicity.
1 Cf. Weyl, op. cit., pp. 115 f.; English edition p. 155. See also section 42 below.