At this point, as science began to affect people’s material lives, it inevitably began to affect their deeper ways of thinking. For many people who were trying to hang on to a traditional style of faith, some of the large-scale changes to the generally held ways of thinking that most people had subscribed to for so long were not happy changes. The same still holds true today.

                                        René Descartes.

A younger contemporary of Bacon was the man many still see as the leading light of the Renaissance and its new way thinking, a sickly French parochial-school boy who became a sickly man with a mind like a razor: René Descartes. He spent years manoeuvring to get a feel for what the religious leaders of his time would let him say, and only then did he publish his views on how thinking and learning should be done.

Descartes separated science from religion and morality. Under his model, science can advance our ways of dealing with the physical world of the body, but religion and its inherent morality must still oversee the activities of our minds and souls. For the people of his time, the affairs of souls were seen as being much more important than those of bodies or anything else made from matter. Under Descartes’s model, religion retains primary control over our decisions about what we should be doing with our lives, including how we should be using the findings of science.^3,4

Descartes’s clever manoeuvre then enabled him to separate the mind from the body and the realm of thought from the realm of faith. It was a move that somewhat ameliorated the religious authorities’ scrutiny of those who studied the physical world and how the things in it worked, but he only delayed the inevitable. Because we humans have issues and concerns in both realms, the sensory and the abstract, sooner or later we would have to deal with the logical conclusion that the two realms had to interact somehow in order for them both to involve and make sense to us.

Describing all the ways in which science sometimes eroded, and sometimes blasted, the traditional beliefs of the majority of people would fill a whole encyclopedia. We can be content with looking at just three such ways. I chose these three because I believe they are paradigmatic, as did Freud.⁵

              Galileo Galilei, physicist, mathematician, engineer, astronomer, and philosopher

First, the astronomers shook the traditional view of the heavens. In 1543, Copernicus proposed a new model of our universe. Instead of the earth being at the centre with the rest of the heavenly bodies like the sun, the moon, the planets, and the stars revolving around it, he said the sun was at the centre of our solar system, and the earth was just one more planet—along with Mercury, Venus, Mars, Jupiter, and Saturn—revolving around the sun. Supposedly, his idea was proposed only for discussion purposes so he was not attacked by the religious leaders of his time. But in the 1600s, Galileo and, later, Newton took up and refined the Copernican model. They discovered a set of natural laws that described both events in the cosmos and events on the earth in subtle mathematical formulas that gave precise predictions about phenomena like falling objects, fired cannonballs, eclipses, comets, and planetary orbits—phenomena that had previously been given only inaccurate, conceptually messy, ad hoc explanations.

Today, Galileo and Newton’s picture of the solar system and how it works seems intuitive and obvious to most people. But Galileo in his time was seen by religious leaders as a demon. The Bible said God had made man as his special, darling creation. The earth had been created, along with all of its life forms, as a special home for us. Thus, the earth had to be the centre of the universe. Ptolemy also had said so, over a thousand years before, and his model of the cosmos fit neatly together with the teachings of the Church. Besides, the sun, the moon, and the stars moved across the sky from east to west. These things would not be possible if the earth were not the centre. What fool could question these obvious truths?

Galileo did and almost paid with his life. He was forced to recant under the threat of horrible torture. Galileo had begun his higher education studying medicine. He knew what they could make him say once they began to apply their racks and thumbscrews. With his telescope to back him up, he tried hard to persuade the pope and his agents that the evidence proved the Copernican model was correct. They weren’t interested; in fact, they became angrier. So he signed where they told him to sign. But according to one version of his story, as he left the building, he pointed up at the moon and said, “It still moves.”

That statement deeply reveals the kind of thinking on which it is predicated. It could stand as a statement of the fundamental belief of science. Material reality is what it is. Our role is to learn about it by observing it, formulating theories about it, and doing experiments to test those theories. We can’t impose our views on reality. If one of our theories goes against what has long been society’s received wisdom on any subject, this contradiction, for scientists, means nothing. What matters is whether it fits the evidence.

Aristotle and the authors of the Bible and even last year’s scientific theories have no more of a monopoly on truth than any one of us. Most crucially, we can always go back to physical reality and test again. Let reality be the arbiter. That is the method and belief system to which scientists are committed. (The Catholic Church pardoned Galileo in 1992, nearly 360 years after his “offence.” The Copernican model of the solar system, the one that Galileo championed, has been generally accepted as the correct model since about 1700.)