‘Realism and anti-realism’ is concerned with the debate between scientific realism and its converse, anti-realism or instrumentalism. Realists hold that the aim of science is to provide a literally true description of the world. Instrumentalists hold that the aim is rather to provide a convenient way of predicting the results of observation and experiment. The ‘no miracles’ argument, one of the strongest arguments for scientific realism, is shown to be a plausibility argument—an inference to the best explanation. Central to the debate between realism and anti-realism is the observable/unobservable distinction; rival accounts of this distinction by the realist Grover Maxwell and the anti-realist Bas van Fraassen are described.