For the Middle Ages, natural laws had been universal moral rules established by God. The injunction against murder, recognized by all cultures, was a typical example of a natural law. The concept of a physical law of nature was completely absent. That came only as Christian thinkers extended God’s legislative power to the natural world. As philosopher and scientist René Descartes (1596–1650) expressed it, “God alone is the author of all the motions in the world.” For its time, this was a radical