"The peace that passes all understanding" is felt when there is a cessation of the striving for other, striving to understand, striving to know. Thoughts are seen to be empty, hollow, not even nothing underneath, as "nothing" too is a thought. It's seen that there is no knower as thought seems to create that too. Nothing can be or needs to be understood, as what seems to be understanding is also thought. There is no concern about thought whatsoever, no trying to control it, as the attempt to control thought is thought. It's seen clearly that thought belongs to no one, as a seeming one for whom it would belong is itself thought. It's like the mind, or thought stream sort of rests in itself as it's somehow known that it goes nowhere, knows nothing and names nothing.....completely impersonal, yet it's all there is of me, and you.