Scientific realists believe that highly confirmed scientific theories and explanations should be accepted as at least approximately true. The concept of truth, in the view of most contemporary realists, should be interpreted as some kind of correspondence relation between the scientific statements that are said to be true and the states of affairs obtaining in a mind-independent, objective reality. Thus, realists take well-tested scientific theories (models, explanations) to be representations of a reality that exists independent of the categories and concepts of the human mind. They must therefore defend a combination of metaphysical and epistemological theses. The metaphysical thesis says that there is a mind-independent reality, and that it is somehow structured independent of scientists' concepts. The epistemological thesis is that the human mind has access to this reality.

Today, scientific realism has to face three different kinds of antirealist opponents. First, instrumentalists hold that the pragmatic purpose of scientific theories is not to represent a mind-independent world, but to allow us to orient in and interact with the world in which we find ourselves, for example, by predicting future experiences. In this spirit, Bas van Fraassen (1980) has defended the view that to accept a scientific theory means to accept it as empirically adequate, not as true (this claim is normative, not descriptive of actual scientific practice). For somewhat different reasons, Alex Rosenberg (who is a realist about physical theories) has developed an instrumentalist account of biology (Rosenberg 1994).