Eurisko (Gr., I discover) is a program written by Douglas Lenat in the Lisp programming language. A sequel to Automated Mathematician, it consists of heuristics, i.e. rules of thumb, including heuristics describing how to use and change its own heuristics. Lenat was frustrated by Automated Mathematician's constraint to a single domain and so developed Eurisko; his frustration with the effort of encoding domain knowledge for Eurisko led to Lenat's subsequent (and, as of 2006, continuing) development of Cyc. Lenat envisions ultimately coupling the Cyc knowledgebase with the Eurisko discovery engine.
Development commenced at Carnegie-Mellon in 1976 and continued at Stanford University in 1978 when Lenat returned to teach. "For the first five years, nothing good came out of it," Lenat said. But when the implementation was changed to a frame language based representation he called RLL (Representation Language Language), heuristic creation and modification became much simpler. Eurisko was then applied to a number of domains with surprising success, including VLSI chip design.
Lenat and Eurisko gained notoriety by submitting the winning fleet to the United States Traveller TCS national championship in 1981, forcing extensive changes to the game's rules. After Eurisko won again in 1982, tournament officials announced that if Eurisko won another championship the competition would be abolished; Lenat retired Eurisko from the game. The Traveller TCS wins brought Lenat to the attention of DARPA, which has funded much of his subsequent work.