We don’t often associate science with conversations. Science interviews are usually short media exercises, and science seems too serious and rigorous to be approached by unstructured dialogue. “As Far as We Know”, a series of radio discussions about science between a distinguished broadcaster (Kim Hill) and equally distinguished scientist (Paul Callaghan), is not a work of science. But it does have a serious aim: to answer the question “What is science?” It may not answer the question to everyone’s satisfaction. But it does show the power of conversation to illuminate – and lighten up – science. So what is science, according to this book? It is, says Callaghan, a “means of looking at the world to try to understand natural phenomena and their causes in a way that is self-consistent and corresponds to reality.” Callaghan sees a sharp line between what is science and what is not, and doesn’t miss many opportunities to draw it. In this book, creationism, homeopathy, and phone cancer...