  There are two different lines of thinking about the role of fictions in science. According to one, all models are fictions. This line of thinking is motivated by considering the role, for example, of “the ideal pendulum” in science. Scientists, it is argued, often make claims about these sorts of entities (e.g., “the ideal pendulum has a period proportional to the square-root of its length”) but they are nowhere to be found in the real world; hence they must be fictional entities. This line of argument about fictional entities in science does not connect up in any special way with computer simulation—readers interested in this topic should consult the entry on  -->scientific representation-->  [forthcoming].