Permutation argument against Metaphysical realism

Realism is an intuitive idea which most people accept explicitly or implicitly. It is hard to find someone who does not accept mind-independent things or the relation between truth and states of affairs; however، how the connection between language and reality can be stated is a controversial issue، at least among philosophers. Based on the most popular theories about the problem، there is a direct correspondence between lingual elements and external world. At first glance، it seems acceptable، like many other intuitive ideas، but further examination reveals some dissatisfactions. Hilary Putnam، well known American contemporary philosopher، has criticized such a point of view (‘Metaphysical Realism’ as he has called)، partly using model theoretic based arguments. Model theory is a branch of mathematical sciences which studies the connection between a language and its interpretations. This paper attempts، less technical and more intuitive، to examine Putnam''s Permutation argument in which he uses model theoretic concepts and theorems to show that Metaphysical Realist is not able to fix reference of the elements of language via fixing truth value of the whole sentence in which those elements appear.