popper-logic-scientific-discovery

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new appendices
physical theory has reached a depth of insight utterly beyond the
Cartesian approach.
It seems to me that the doctrine that the laws of nature are in no sense
contingent is a particularly severe form of a view which I have described
and criticized elsewhere as ‘essentialism’. 13 For it entails the doctrine of
the existence of ultimate explanations; that is to say, of the existence of
explanatory theories which in their turn are neither in need of any
further explanation nor capable of being further explained. For should
we succeed in the task of reducing all the laws of nature to the true
‘principles of necessitation’—to truisms, such as that two essentially
extended things cannot take up the same extension, or that nothing
which is red is also green—further explanation would become both
unnecessary and impossible.
I see no reason to believe that the doctrine of the existence of ultimate
explanations is true, and many reasons to believe that it is false. The
more we learn about theories, or laws of nature, the less do they
remind us of Cartesian self-explanatory truisms or of essentialist definitions.
It is not truisms which science unveils. Rather, it is part of the
greatness and the beauty of science that we can learn, through our own
critical investigations, that the world is utterly different from what we
ever imagined—until our imagination was fired by the refutation of
our earlier theories. There does not seem any reason to think that this
process will come to an end. 14
All this receives the strongest support from our considerations about
content and (absolute) logical probability. If laws of nature are not
merely strictly universal statements, they must be logically stronger than
the corresponding universal statements, since the latter must be
deducible from them. But the logical necessity of a, as we have seen (at the
end of appendix *v) can be defined by the definiens
p(a) = p(a, ā) = 1.
For universal statements a, on the other hand, we obtain (cf. the same
appendix and appendices *vii and *viii):
13 Cf. my Poverty of Historicism, section 10; The Open Society, chapter 3, section vi; chapter 11;
‘Three Views Concerning Human Knowledge’ (now in my Conjectures and Refutations, 1965,
chapter 3) and my Postscript, for example section *15 and *31.
14 Cf. my Postscript, especially section *15.