Mouroulis replies: Albert Einstein wrote, “The justification (truth content) of the system [physics] rests in the proof of usefulness of the resulting theorems.” 1
Robert Reiland argues that only specific deductions from a theory, not the theory itself, can be tested to be true. I confess I fail to see the usefulness of that distinction. Newtonian mechanics or electromagnetic theory can be seen as false, as outside the categories of true and false, or as true within their sphere of applicability. I believe the third view has the most value.
Reiland says a theory that makes an infinite number of predictions can never be shown to be true through any necessarily finite number of tests. Does it therefore have a truth content of zero? Einstein’s view implies that when a large number of positive tests have accumulated (and obviously in the absence of negative tests for a core prediction), the theory has achieved high truth content. My statement that the aim of every scientific theory should be to have its truth proven was only meant to imply that experimental verification should not be abandoned, especially not on any a priori philosophical grounds about the nature or quantity of attainable truth.
According to Reiland’s other argument, a scientific theory connects concepts that derive meaning from it; hence the theory cannot be known as factual. Yet a look at sciences other than physics would reveal that this does not hold for all of “our concepts in science.” To give one example, should geological theories be factual or should they merely connect concepts that derive their meaning from the theory? Do earthquakes derive their meaning from geological theories?
Although Reiland makes some fine distinctions about the role of theories, it is not clear that those distinctions extend beyond a specific set of physics theories. The difference between that set and theories in other areas of science probably has to do with the degree to which they are remote from everyday experience and deserves further exploration in a different forum. However, I still think it is useful to assign truth content to scientific theories; otherwise, one risks lapsing into metaphysics.
