The classical, as in old fashioned, 70s, 80s definition of AI is solving any problem using heuristics. This is contrasted with algorithmic problem solving; whic

The classical, as in old fashioned, 70s, 80s definition of AI is solving any problem using heuristics. This is contrasted with algorithmic problem solving; which is impossible to do if your problem is intractable (you can't have an efficient 3SAT solver if you don't use heuristics). The canonical example is CSP (constraint satisfaction problem) solvers: people legit thought, encoding knowledge in a Prolog-like CSP solver will allow us to create AI. AI researchers before the "AI Winter" thought AI is all about encoding the information in a way computers can use heuristic to solve problems like humans.