4042. From this one may now see that through the human being alone is a descent from the heavens into the world possible, and an ascent from the world into the heavens. It is the brain and the interior parts of it by which the descent and ascent is effected; for there in the brain reside the very beginnings, or the first and final ends, from which every single thing in the body emanates and is derived. There also is the source of the thoughts which belong to the understanding, and the source of the affections which belong to the will.