  The early development of conflicting theories about the microscopic mechanism
of High Temperature Superconductivity is described. The biographical roots of
this diversity are stressed, as well as its subjective/objective roots. This
study of a specific case of knowledge about a specific fact of nature allows to
discuss the subjective and objective roots of scientific pluralism. Relativism,
the Duhem-Quine thesis on the underdetermination of theory by facts, are
discussed from the stand point of the materialist view on the dialectics of
knowledge and nature. Developments of dialectic materialism seem to be
suggested by this study.
