Chapter 1 - The Reach of Explanations.md : The physicist Galileo Galilei was perhaps the first to understand the importance of experimental tests (which he called cimenti, meaning 'trials by ordeal') as distinct from other forms of experiment and observation, which can more easily be mistaken for 'reading from the Book of Nature'. Testability is now generally accepted as the defining characteristic of the scientific method. Popper called it the 'criterion of demarcation' between science and non-science. #L3