Does anyone know of Hakuin and 'the great doubt'?

Question

Was it a boundless and inexpugnable realization or 'coming to'?

Answer 1

I know a bit about Hakuin, but I'm not familiar with "the great doubt."

However, I looked it up, and my understanding--cursory as it is--is that a sudden realization comes upon a student of Zen after a perhaps years-long process of coming to.

So, it's both.

Which, given the practice of Zen, is fitting.