Nicholas Rescher argues in Unknowability that there are certain things that logically cannot be known, such as “an idea that will never occur to any human being.”
Prominent among unknowables are the unknowables of science. Given the way scientific research and discovery work, it is impossible for present science to anticipate future science, or even to understand it. The reason is that “every new discovery opens the way to others, every question that is answered gives rise to yet further questions to be investigated. . . . Our questions - let alone answers - cannot outreach the limited horizons of our concepts. Having never contemplated electronic computing machines as such, the ancient Romans could also venture no predictions about their impact on the social and economic life of the twenty-first century. Clever though he unquestionably was, Aristotle could not have pondered the issues of quantum electrodynamics. The scientific questions of the future are - at least in part - bound to be conceptually inaccessible to the inquirers of the present” (12).
Discoveries open up questions that we didn’t consider before the discovery, so that “New scientific questions arise from answers we give to previous ones, and thus the issues of future science simply lie beyond our present horizons” (13).
The conceptual landscape can be so radically altered that “the workers of a substantially earlier period (however clever) not only have failed to make but which they could not even have understood, because the requisite concepts were simply not available to them” (14-15).
This is why scientific breakthroughs has such a difficult time getting accepted. As Rescher puts it, “”Science forecasting is beset by a pervasive normality bias, because the really novel often seems so bizarre” (15). He offers the example of Newton’s discovery of gravitational action at a distance: “If there was one thing of which the science of the first half of the seventeenth century was confident, it was that natural processes are based on contact-interaction and that there can be no such thing as action at a distance. Newtonian gravitation burst upon this scene like a bombshell.” Newton’s apologists had a difficult time making Newton’s theory sound plausible: “Roger Cotes explicitly denied there was a problem, arguing (in his Preface to the second edition of Newton’s Principia) that nature was generally unintelligible, so that the unintelligibility of forces acting without contact was nothing specifically worrisome” (16).
Another reason scientific futures cannot be anticipated is that discovery often takes place by accident. Rescher puts it clverly: “Natural science is simply too opportunistic to be fastidious about its mechanisms,” and he cites examples: “eighteenth-century psychologists ruled out hypnotism; nineteenth-century biologists excluded geophysical catastrophes. Twentieth-century geologists long rejected continental drift.” Today, parapsychology is considered unscientific, but who knows? (17-18)