The story is told of a medieval student who, having detected spots in the sun, announced his discovery to a learned man. “My son,” said the latter, “I have read Aristotle many times, and I assure you there is nothing of the kind mentioned by him. Be certain that the spots which you have seen are in your eyes and not in the sun.

Since the very beginning of rational thought, there have been two opposing trends: idealism and materialism …
Idealism is on the side of order. Its champion in ancient times was Plato, who argued that the truth was beyond question, and that those of inferior ranks were not fit to understand the complexity of natural philosophy. Today’s idealists argue the same thing in modern form. The aim of science, from this viewpoint, is to conserve, to explain the universe at large, and to suggest in elaborate and sophisticated ways that the sole purpose of communicating science is so that the public appreciate the status of science and scientists.
Materialism is practical and experimental. For centuries, the materialist view did not gain support in cultured circles, because of its revolutionary potential, the same potential that was realised in the Renaissance. It is fundamentally a philosophy of matter in motion, an account of nature and society from below rather than above. It is a philosophy that realises the power of change through getting to know nature’s ground rules.
The very continuation of the struggle … suggests that it is … a reflection of political struggles in the scientific sphere. At various times, idealism has been used to justify an existing state of affairs. And at each stage, materialism has called upon a practical test of reality and on the necessity of change.