The premise of this short book seemed unpromising: a physicist with no formal training in classics or history was apparently claiming that Anaximander, a Greek philosopher about whom almost nothing is known, is the spiritual father of modern science. But, in the event, it was much better than I'd expected. Rovelli is certainly not a historian, but he appears to know Latin and Greek, has read widely, and had enough interesting things to say that he kept me thoroughly entertained. I started this afternoon at Luton airport, and didn't put it down until I finished just now in Geneva.
A large part of the book is concerned with the question of what "science" is, and in what ways it differentiates itself from religion. Rovelli's central argument is that the distinguishing mark of science is that it is always willing to question established authority. This, above all, is why he wants to argue that Anaximander should be considered the founder of the scientific tradition. Anaximander's teacher, according to later authors, was Thales of Miletus; but rather than simply accepting his master's ideas as holy writ and further developing them, Anaximander changed them in many important ways. Even if the story is just a myth - Rovelli is happy to admit that the facts are extremely uncertain - I think he has a good point. This way of reasoning about things is historically unusual. The philosophical/scientific tradition may not have started exactly here, but it began around this point in time, and, if nothing else, Anaximander is a nice way of symbolizing the break with what had gone before.
The book has many thought-provoking examples that I had not previously come across; here is the one I liked most. Rovelli is discussing the question of cultural relativism. Different societies have different belief systems, and on what grounds can we say that one is "better" or "more true" than another? It is fashionable, at least in some circles, to say that the terms make no sense. But Rovelli has a nice case study concerning the Greek mathematician Eratosthenes, who accurately measured the circumference of the Earth in the third century B.C. by comparing the shadows cast at widely separated locations. This part of the story is famous; what I hadn't heard was that a Chinese astronomer performed the same experiment several centuries later, but reached completely different conclusions. The Chinese believed that the Earth was flat, so the astronomer, seeing the different shadows, thought that he had determined the distance to the Sun, which would have been quite close. The interesting thing is what happened when the Chinese and Western traditions finally collided in the early 17th century. The Westerners just smiled at the misapprehensions of the Chinese astronomers; the Chinese, on the other hand, rapidly agreed that they had got it wrong. There was no question of the two accounts being different but equally valid.
If you are interested in the faith/science debate, you may also enjoy Rovelli's book. He comes across as a pleasantly intelligent and open-minded person, something that is unfortunately all too rare in this area.