It seems to me that most philosophers of science use the term ‘accepted’ or ‘acceptable’ as a substitute for ‘believed in’ or ‘worthy of being believed in’. There may be a lot of theories in science that are true and therefore worthy of being believed in. But according to my view of the matter, this worthiness is no concern of science. For science does not attempt positively to justify or to establish this worthiness. On the contrary, it is mainly concerned with criticizing it. It regards, or should regard, the overthrow of even its most admirable and beautiful theories as a triumph, an advance. For we cannot overthrow a good theory without learning an immense amount from it and from its failure. As always, we learn from our mistakes.
The overthrow of a theory always creates new problems. But even if a new theory is not yet overthrown, it will, as we have seen from the example of Bohr’s theory, create new problems. And the quality, the fertility, and the depth of the new problems which a theory creates are the best measures of its intrinsic scientific interest.
To sum up, the question of the acceptance of theories should, I propose, be demoted to the status of a minor problem. For science may be regarded as a growing system of problems, rather than as a system of beliefs. And for a system of problems, the tentative acceptance of a theory or a conjecture means hardly more than that it is considered worthy of further criticism.