What really happened with Galileo and Darwin?
From John Polkinghorne’s masterly book Science & Theology.
Born in 1564, Galileo Galilei is unquestionably one of great figures in the history of science. He repudiated mere appeal to the authority Aristotle and in its place pioneered the investigative technique of combining mathematical argument with an appeal to observation and experiment. His orderly and use of the newly discovered telescope as a means the searching the heavens (resulting in the discovery of mountains on the moon, spots on the sun, satellites encircling Jupiter, and the phases of Venus) reinforced his belief in the Copernican system. By 1616 this had got him into trouble with the Vatican authorities, who believe that the Ptolemaic system, with its fixed Earth, was endorsed by the Bible. Some kind of accommodation which worked out between Galileo and his chief critic, Cardinal Belarmine. The exact terms of this agreement later became a matter of dispute and there is continuing scholarly debate on the question. The point at issue is whether Galileo was simply told not to espouse or defend our the Copernican principle or whether he was also forbidden to teach it in any way whatsoever. Whatever the rights of the matter, intellectual freedom was clearly curtailed by the exercise of ecclesiastical authority.
In the 1632, Galileo published his Dialogue Concerning the Two Chief World Systems. Cast in the apparent form of an even-handed discussion of the pros and cons of the ideas of Ptolemy and Copernicus, its actual presentation of the case for Copernicanism was so overwhelming that it was clearly a tract in that system`s defense. Moreover, Simplcio, the defender of Ptolemy, was not only weak in argument and something of a buffoon, but he also stated, almost word for word, points of view which had been propounded by the current Pope, Urban VIII. It is scarcely surprising that the authorities were upset and they responded by summoning Galileo to appear before them. He was sentenced by the Inquisition to life imprisonment, immediately commuted by the Pope to continuing house arrest. At no stage was Galileo subjected to torture.
No one can claim that this is at an edifying story or that the church authorities displayed wisdom or intellectual integrity in their implacable opposition to Galileo’s Copernican ideas. (The Roman Catholic ban on Copernicanism was rescinded in 1820, but Galileo’s condemnation was only recently abrogated formally.) Yet the issues were complex and the illumination afforded by hindsight should not result in our painting the scene in stark black and white. There were scientific difficulties in the case presented by Galileo. One was the absence of the stellar parallax — the shift in the current position of the stars expected to result from than being viewed from different perspectives defeat of whether moving around and orbit in the course of the year. (We now know that this was not observable with 17th century resources because the stars are so very distant from us.) Galileo placed great emphasis on the claimed confirmatory value of his explanation of the tides. We now know that he was completely in error about this matter. He even ridiculed Kepler when the latter suggested that the moon might have some relevance for tidal phenomena!
Throughout the controversy, and until his death, Galileo remained a religious man. Many of his discussions with his opponents had focused on the right way in which to read the Bible. Galileo genuine evaluate its spiritual authority, but the fact that it is written in language intended to be understood by common people meant, in his opinion, that it was illegitimate to try to read advanced physical theory out of its pages. If there was an apparent conflict between the surface meaning of words of Scripture and the results of science, Galileo believed that the should encourage us to seek a deeper understanding of the relevant biblical passage — a view for which he could appeal to the support of St. Augustine, no less.
Cardinal Bellarmine had urged upon Galileo the view that mathematical theories like that of Copernicus, were just means of ‘ saving the appearances’, that is to say that they were calculational devices and not necessarily to be taken seriously as literal descriptions. Here we have an engagement with one of the fundamental questions in the philosophy of science, to which we will subsequently returned. Are scientific theories just convenient manners of speaking, or do they describe the physical world as it actually is?
Finally, there were the personal aspects of the controversy: Urban VII’s wounded pride, Galileo’s brilliant but polemically shrill use of the Italian language, the ambitions of Galileo’s opponents amongst the Jesuit astronomers (to this day effective participants in the scientific community). These varied considerations do not mean that the Roman Catholic authorities did not make a bad mistake. Of course they did, but in complex and cloudy circumstances. The Galileo affair by no means indicates that there is an inevitable incompatibility between science and religion. One unwise incident does not imply a continuing conflict.