That's a good point. Guess-and-verify could be a handy additional heuristic method if Mathematica's other methods came up empty on a problem. I've also heard of

That's a good point. Guess-and-verify could be a handy additional heuristic method if Mathematica's other methods came up empty on a problem. I've also heard of machine learning being used to choose between internal algorithms available in formal proof systems, to try to pick the algorithm that's most likely to work instead of just trying them all sequentially.