Classicly

In metaphysics are many points equally indeterminable. Here a man’s own mind is the field of observation, in every part of which the most rigid, extensive, and patient scrutiny, and the most careful comparison have been made by the most profound thinkers, and with the best lights; but up to this time there are many points unillustrated, undecided. Will they ever be made more plain? Who does not feel that there are doubtful points in himself that he will never understand, at least this side of the grave?