A scientific revolution does not only create new knowledge. It also generates new ways of thinking, new ways of asking questions, and new ways of answering them. Before the scientific revolution at the beginning of the seventeenth century, when questions were raised, for example, about whether or not blood circulated in the body, people looked for answers in the ancient texts. Aristotle and Galen taught that blood did not circulate in the body; therefore, the question had been answered. How did Aristotle and Galen know what they knew? That question was not posed. They were more knowledgeable than us, and that was sufficient.