Edinburgh School's theory of natural rationality, enunciated to render symmetrical explanation plausible, thereby providing support for its relativism, is presented and evaluated. I have endeavoured to demonstrate that there are gross misinterpretations of Hesse's theory of science, network model, and her conceptions of classification of objects and of universals; that Edinburgh School's theory of natural rationality suffers from a considerable area of ignorance concerning its foundation. I have further shown that not only the theory is not descriptive of the actuality (...) of people's reasoning, but it in fact is normatively laden. Even if these problems can be overcome, I have shown that it ultimately does not render all beliefs equivalent insofar as rationality status is concerned, and hence symmetrical explanation will still not be possible. Concerning the Edinburgh School's interest theory, I have argued that there are some incoherencies in the proposed positions; and that even if these are rectified the resulting theory leads to grotesque absurdities. (shrink)