Our previous book, About Life, concerned modern biology. We used our present- day understanding of cells to ¿define¿ the living state, providing a basis for exploring several general-interest topics: the origin of life, extraterrestrial life, intelligence, and the possibility that humans are unique. The ideas we proposed in About Life were intended as starting-points for debate ¿ we did not claim them as ¿truth¿ ¿ but the information on which they were based is currently accepted as ¿scientific fact¿. What does that mean? What is ¿scientific fact¿ and why is it accepted? What is science ¿ and is biology like other sciences such as physics (except