What is Real?: The Unfinished Quest for the Meaning of Quantum Physics

by Adam Becker

The realists also argued that the distinction between what is observable and what is unobservable was neither meaningful nor relevant to science. This, of course, was anathema to the positivists. Some positivists had even gone so far as to say that objects seen in microscopes were not truly real, because they were not “directly” perceived. The scientific realists thought this was preposterous. “If this analysis is strictly adhered to, we cannot observe physical things through opera glasses, or even through ordinary spectacles, and one begins to wonder about the status of what we see through an ordinary windowpane,” wrote Grover Maxwell, one of the most vocal defenders of scientific realism. Maxwell also pointed out that the very idea of something that is “unobservable in principle” is subject to revision with new theories and new technology. Before the development of optics and the microscope, he pointed out, something “too small to be seen” would have been unobservable in principle. “It is theory, and thus science itself, which tells us what is or is not … observable,” Maxwell wrote, echoing Einstein’s words to Heisenberg. “There are no a priori or philosophical criteria for separating the observable from the unobservable.”

The wrong turn/the extreme position