Suppose you install two different chess-playing programs on your computer and yoke them together with a little supervisory program that pits them against each other, game after game, in a potentially endless series. Will they play the same game, over and over, until you turn off the computer? You could set it up like that, but then you wouldn’t learn anything interesting about the two programs, A and B. Suppose A beats B in this oft-repeated game. You couldn’t infer from this that A is a better program in general than B, or that A would beat B in a different game, and you wouldn’t be able to learn anything from the exact repetition about the strengths and weaknesses of the two different programs.
What does this intuition pump accomplish? It takes the familiar phrase “could have done otherwise” and shows that contrary to widespread but ill-examined opinion, a valuable version of it does not depend on indeterminism. If there is a sense of “could have done otherwise” that is both incompatible with determinism and morally important—not merely a metaphysical curiosity, you might say—this has yet to be established, and the burden of proof lies with those who think so. One more “obvious” point exposed as not so obvious after all.
Source:
Philosopher Daniel Dennett’s Book Intuition Pumps