'What if it is disease?'

he decided at last. 'What does it matter that it is an abnormal intensity, if the result, if the minute of sensation, remembered and analyzed afterwards in health, turns out to be the acme of harmony and beauty, and gives a feeling, unknown and undivined till then, of completeness, of proportion, of reconciliation, and of ecstatic devotional merging in the highest synthesis of life?'
(...)
He could not doubt, and could not admit the possibility of doubt.
(...)
Since at that second, that is at the very last conscious moment before the fit, he had time to say to himself clearly and consciously, 'Yes, for this moment one might give one's whole life!', the wothout doubt that moment was really worth the whole of life.

Myshkin, The Idiot, FD