Bas van Fraassen, in his chapter on realism distills a definition of realism from a group of statements made by Willfred Sellars, Brian Ellis, Hillary Putnam, Michael Dummett and Richard Boyd. I will only include here two of the statements by Hillary Putnam, who is one of the most frequently cited writers on scientific realism (Braver 2007: 14).
A realist (with respect to a given theory or discourse) holds that (1) the sentences of that theory are true or false; and (2) that what makes them true or false is something external--that is to say, it is not (in general) our sense data, actual or potential, or the structure of our minds, or our language, etc.
That terms in mature scientific theories typically refer (this formulation is due to Richard Boyd), that the theories accepted in a mature science are typically approximately true, that the same term can refer to the same thing even when it occurs in different theories--these statements are viewed by the scientific realist...as part of any adequate scientific description of science and its relations to its objects" (van Frasseen 1980: 1067).
These two statements contribute important elements to van Fraassen’s own distillation of what scientific realism means, mainly the notions of what truth is and what it means to accept a scientific theory. Van Fraassen’s definition of scientific realism, then, is this:
Science aims to give us, in its theories, a literally true story of what the world is like; and acceptance of a scientific theory involves the belief that it is true (p. 1066).
Van Fraassen construes this definition as the minimum necessary for the scientific realist to maintain his position of realism.
Ian Hacking says about anti-realism
We construe theories about tiny states, processes and entities only in order to predict and reproduce events that interest us (p. 21).
According to this anti-realist view, science does not aim to provide us with a literally true story about what the world is like, and theories are only meant to serve our human interests, not to literally represent our world. However, when van Fraassen defines anti-realism, he contends that scientific language should be construed literally, for there is no other way to take them. They are not metaphors, similes, or analogies. Van Fraassen (1980) defines scientific anti-realism as:
a position according to which the aim of science can well be served without giving such a literally true story [as given by realists], and acceptance of a theory may properly involve something less (or other) than belief that it is true (1067).
Braver, Lee. 2007. A Thing of This World. Evanston, Ill.: Northwestern University Press.
Hacking, Ian. 1983. Representing and Intervening. Cambridge: Cambridge University Press.
Van Fraassen, Bas. 1980. “Arguments Concerning Scientific Realism” in Philosophy of Science. edited by Martin Curd and J A Cover. New York: W.W. Norton.