Tanya for the 18th of Elul, י''ח אלול

This “lower soul” naturally inclines to “lower” (i.e., corporeal) matters so that even its intellect goes only as far as understanding the composition, and so on, of mundane things. For although the kelipah, which is the source of this soul, is kelipat nogah, a kelipah whose darkness is relieved by a ray of good, nevertheless, it is wholly bound up with mundanity.