David Wootton's Galileo: Watcher of the Skies (Yale, £25) portrays a far more radical character. Contrary to the received scholarship of the last few centuries, Wootton claims that Galileo was not a Catholic, nor even a Christian, but some sort of deist who believed that a god might have created the universe but has since left it well alone. Wootton's grounds for this conjecture are quite shaky. Galileo's surviving private correspondence points to him being what he always claimed to be: an observant Catholic. Wootton must rely on an effective cover-up of all the contrary evidence. But it seems likely that Galileo was not especially devout, which explains why one of his more pious friends got so excited when the great man appeared temporarily to cultivate a more personal faith in his old age.
Despite its unwarranted speculation about Galileo's religious unbelief, Wootton's biography has much to recommend it. It is engagingly written and offers fresh insights into Galileo's intellectual development. That Wootton passes over some of the mathematical aspects of Galileo's achievement must be accounted an advantage of this book if it is picked up by a non-specialist.
Heilbron makes no such concessions to his readers. His book is packed with diagrams and seeks to understand Galileo's work as the great man saw it. Galileo was a philosopher, not a scientist. He sought to solve problems from first principles and used experiments only to demonstrate his solutions. In contrast, modern science deals with hypotheses that experiments can falsify but not prove.
Galileo's observations certainly reordered the universe. But did he also help to banish God from men's minds? The evidence would suggest not. To Johannes Kepler, whose spectacularly accurate astronomical tables based on elliptical orbits effectively proved that the Earth moves, science was a sacred duty. His scrawled notes contain spontaneous prayers and he always gave thanks to God for his achievements. Robert Boyle and Isaac Newton were both even more concerned with religion than they were with science. And both were convinced that there could be no conflict between faith and reason.
Even in the 19th century, it was the discovery of historical errors in the Old Testament, rather than science, which caused the Victorian crisis of faith. And the tragic death of his young daughter Annie destroyed the last vestiges of Charles Darwin's Christianity. It had already been severely weakened by the thought of his rationalist father burning in hell. The problem of suffering is, and always has been, the biggest challenge to faith in a loving God. Just ask Job.
Today, only a minority of scientists are religious believers and the evidence suggests that the more eminent the scientist, the graver his doubts. But modern science can discomfit the atheist just as much as the Christian. A century ago, it was scientific orthodoxy that the universe could have no beginning, just as Aristotle had always said. For Fred Hoyle, the avuncular Cambridge physicist, this was almost an article of faith. When a Belgian Jesuit by the name of Georges Lemaître suggested that time and space originated at a singularity, Hoyle disparaged the theory as postulating a "big bang". Later, it transpired that Lemaître and, incidentally, Christian doctrine were correct. The universe is not eternal.
Nonetheless, Stephen Hawking's new book The Grand Design (Bantam Press, £18.99) says that even though the universe started with a bang, God was not required to light the blue touch paper. All that is needed is a working theory of gravity and the universe will make itself spontaneously. This is true enough, but Hawking has forgotten the lesson Galileo wanted to teach the Catholic Church: science cannot threaten religious truth. The origin of the universe requires that the laws of physics exist and these laws do not explain themselves. A divine legislator still has something to do. That the universe appears fine-tuned to allow for the appearance of intelligent life suggests He did it rather well.
