‘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 true description of the world. Anti-realists hold that it is to provide a true description of the ‘observable’ part of the world. 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 and the views of realist Grover Maxwell and anti-realist Bas van Fraassen are described. The underdetermination argument is also explained.