Darwin used his rational mind to pursue a hunch. From what I’ve read of Einstein he was much the same. He had a sense of an idea, and then had to set about figuring out how explain it and ways figure out how to prove whether it was right or wrong.

I’ve heard Lawrence Krauss talking about the same thing being a driving force with many great theoretical physicists. Their mind get ms hung up on a possibility or an idea, and can’t quite figure out how to lay it out in a way that it can be tested, but eventually they or somebody else does figure it out. Sometimes they are proven right and sometimes wrong. Either way, our understanding of the world progresses.

The guy who had an “aha” moment and figured out the double helix structure of DNA, was tripping on Acid when it first occurred to him.