Pierre Duhem, the eminent French physician, scientific historian, and philosopher of science, claims that scientific theory is a conventional system, a description of relations among external things, and it is also an integrity, including the basic assumptions, principles and rules.Having experienced numerous scientific practices, he improved the theoretical framework(s) of symbolism about science, and of realism about relation.He and his works is highly epistemological and methodologically significant in the field of history and philosophy of science.