Since according to Feyerabend scientific practice at its best does not go by any set norms, we cannot discourage any theory which might go against the so-called well-known facts. Calling himself an anarchist, Feyerabend vehemently argues that any approach or view, however bizarre and eccentric, has the right for continued existence. That is to say, a view which goes against the well-known facts has as initial justification as the view which is consistent with the known facts. Instead of killing a new theory just because it goes against known facts, we must allow it to grow or to die a natural death consequent upon its failure to build for itself an empirical basis. Thus, Feyerabend very effectively pleads for tolerance in the case of those theories which may not find support from what we already know.

It may be mentioned against Feyerabend that such a tolerance will lead to the mushroom growth of theories. Feyerabend accepts this consequence of his position as a positive feature. He strongly advocates proliferation of theories. Scientists who work in a certain domain must work with more than one theory since there is no norm which decides beforehand which one of the theories is more plausible. In other words, consistent with his rejection of the idea that there are set norms which guide scientific thinking. Feyerabend calls for pluralism in scientific practice. The idea of one theory at a time has no basis, once it is shown that scientific practice at its creative best has thrown to winds every conceivable norm.

Finally, like Kuhn, Feyerabend maintains that the relationship between successive theories in science is incommensurable. In fact, he provides new arguments in favour of the incommensurability thesis propounded by Kuhn.