A. Newell, and H. Simon. Communications of the ACM, 19 (3):
113--126(March 1976)p. 116: ``The Physical Symbol System Hypothesis. A physical symbol system has the necessary and sufficient means for general intelligent action.'' p. 120: ``Heuristic Search Hypothesis. The solutions to problems are represented as symbol structures. A physical symbol system exercises its intelligence in problem solving by search--that is, by generating and progressively modifying symbol structures until it produces a solution structure.'' p. 121: ``To state a problem is to designate (1) a test for a class of symbol structures (solutions of the problem), and (2) a generator of symbol structures (potential solutions). To solve a problem is to generate a structure, using (2), that satisfies the test of (1).''.