Putnam, Conceptual Relativity, and Metaphysical Realism

Rejecting metaphysical realism (MR) is a basic element in Putnam's Philosophy. He introduces two arguments against MR: Model-theoretic (MT) and brain-in-vat (BIV). However, according to some scholars and commentators who work on Putnam's Philosophy, the phenomenon of conceptual relativity, as introduced by Putnam in some of his books, is another argument by which MR is rejected. This Phenomenon is a state in which two sentences that are at face value incompatible could be consistently true. However, there is not any explicit and complete formulation of this argument in the writings of Putnam and his commentators. In this paper, first we will formulate a version of conceptual relativity against MR. According to our version, Putnam ask the metaphysical realist to explain this phenomenon. Then we will show that this argument is not independent of MT and BIV. Therefore, the phenomenon of conceptual relativity could be an argument against MR only of we accept either MT or BIV. Furthermore, any objection to MT and BIV will weaken the argument from conceptual relativity against MR.