In his own lifetime Galileo was the centre of violent controversy; but the scientific dust has long since settled, and today we can see even his famous clash with the Inquisition in something like its proper perspective. But, in contrast, it is only in modern times that Galileo has become a problem child for historians of science.
The old view of Galileo was delightfully uncomplicated. He was, above all, a man who experimented: who despised the prejudices and book learning of the Aristotelians, who put his questions to nature instead of to the ancients, and who drew his conclusions fearlessly. He had been the first to turn a telescope to the sky, and he had seen there evidence enough to overthrow Aristotle and Ptolemy together. He was the man who climbed the Leaning Tower of Pisa and dropped various weights from the top, who rolled balls down inclined planes, and then generalized the results of his many experiments into the famous law of free fall.
But a closer study of the evidence, supported by a deeper sense of the period, and particularly by a new consciousness of the philosophical underpinning of seventeenth - century science, has profoundly modified this view of Galileo. Today, although the old Galileo lives on in many popular writings, among historians of science a new and more sophisticated picture has emerged. At the same time, our sympathy for Galileo"s opponents has grown. His telescopic observations are justly immortal; they aroused great interest at the time, they had important theoretical consequences, and they provided a striking demonstration of the potentialities hidden in instruments. But can we blame those who looked and failed to see what Galileo saw, if we remember that to use a telescope at the end of the sixteenth century was like playing a modern violin for the first time? Was the philosopher who refused to look through Galileo"s telescope more culpable than those who alleged that the spiral nebulae observed by Lord Rosse"s great telescope in the eighteen - forties were scratches left by the grinder? We can perhaps forgive those who said that the moons of Jupiter were produced by Galileo"s spy - glass if we recall that in his day, as for long afterwards, curved glass was the popular contrivance for producing not truth but illusion, untruth; and if we recall that the concept of an external world was not so much a real concept as a psychological necessity in the minds of seventeenth - century philosophers.
The case of Galileo is sometimes misused to illustrate the thesis that science progresses through the conflict of ideas. But this misrepresents the nature of scientific discovery. The real hero of the story is the slow accretion of the body of knowledge which we call science, and of which Galileo became one of the founders. The most important single aspect of Galileo"s work may have been his demonstration of how fundamental questions about the nature of the world could be answered by the use of instruments. Whether his own methods were completely scientific is open to debate; but that he did have a method is beyond dispute. His method was to make hypotheses, let them stand the test of experiment, and then generalize the results. He was a pioneer in the use of scientific method, which is why we remember him today as one of the great scientists.