Recall that Thomas Kuhn asserted that scientific paradigm change does not carry us ever closer to truth.  A new paradigm, he would say, must resolve generally recognized problems and it must preserve a large part of the problem solving ability of the older paradigm. Science is a unidirectional and irreversible process in the sense that later theories are:

-- wider and scope,
-- more accurate in prediction,
-- and solve more problems,

but still that does not get us closer to the Truth, according to Kuhn, because we can never really be sure about what is out there.  Kuhn writes: "there is no theory independent way to reconstruct phrases like 'really there'." Because of this, Kuhn is inevitably very skeptical of religion -- if you can't know what is "really there," you can't be certain enough of the sacred and of God to have belief in them or make meaningful statements about them.

Barbour, however, writes in counterpoint to Kuhn.  As an epistemological realist, he asserts that you can in some sense know what is "really there."  (Remember here that "epistemology" is the philosophical study of how we know the world, including ourselves.)  Scientists usually assume a realism in the their work -- astronomers, biologists, geologists and chemists all take their theories to represent real events in a real world.  Dinosaurs really did roam the earth; they are not simply useful fictions with which we organize our fossil data.

There are problems, though, with a naive realism that overlooks the role of our minds in the creation of theory.  A naive realism asserts a one-to-one correspondance between theory and the entity it reproduces: that "what you see is what you get," or maybe, "what you think you see is what is really there."  We will see in this class, however, that the abandonment of picturability is one of the most striking features of modern micro and macro physics.  In much of science, a naive realism is just not a viable epistemology.

Barbour's "critical realism" recognizes that while no theory is an exact description of the world (as limited beings, our knowledge of the real must also be limited and partial), the world is nonetheless Real, and events have an objective pattern.  Scientific language and theory do tell us something meaningful and true about the world that is "really there," if only partially using analogies and models of sometimes limited scope.  But the world is real, says Barbour, and it transcends both constructs and data.  Because of this, there can be progress toward truth in science and in all our activities and inquires, and some theories will be better at capturing truth than other theories.  Since you can, in some real sense, know what is "really there," you can be certain enough of the sacred and God to have belief in them and to make meaningful statements about them again.  Barbour's "critical realism" certainly doesn't compell one to become religious -- but it does allow for the possibility of meaningful statements about the sacred and God.

This should help you orient to the issues Barbour is addressing when he writes about critical realism in the text.