How did Grover Maxwell use microscopes and telescopes to challenge the observable-unobservable distinction?

Grover Maxwell challenged the distinction between observable and unobservable entities by highlighting that the concept of the "observable" is not fixed; rather, it depends on the range of available technological devices.1

He noted that many people already rely on aids—such as eyeglasses or contact lenses—to perceive the world clearly. As one moves from the naked eye to magnifying glasses, microscopes, and telescopes, there is an apparent continuum of observation rather than a clear, principled divide. Because there is no objective point along this spectrum where one can definitively mark a shift from "observing" to "inferring," Maxwell argued that there is no logical basis for treating entities viewed through a microscope differently from those seen with the unaided eye. By demonstrating that the boundary is arbitrary and dependent on the tools at hand, he undermined the antirealist reliance on a sharp distinction between observable and unobservable phenomena.12