There is no doubt that realism is an issue. It is no exaggeration to say that realism is characterized in a different way depending on the author who is talking about it, and this is a challenge for anyone who wants to learn what it is. The question, then, of realism or anti-realism is such a controversial issue that a short story will never satisfy the discussion between the realists or anti-realists. To resolve this dilemma, constructivism proposes knowledge as a fundamental aspect of its functionality. Knowledge does not correspond to reality, rather it fits reality or it does not. The metaphysical realist seeks knowledge that corresponds to reality, while the constructivist seeks to fit his theory to what we know of the world. The fit describes the theory's capacity, but not the capacity of the world. When we say something that "fits" (a key in a lock that it opens), this fit describes a capacity of the key and says nothing of the lock.