The Interior Life is the Spiritual Life considered from a human standpoint. It is the return of the Prodigal, the submission of rebellious man to God. It consists in subjecting corrupt nature to the dominion of reason enlightened by faith, or in living in harmony and union with God. The self-conquest and conformity to the divine will, necessary to attain the perfection of the interior life, must extend not only to man's external conduct, but even to his inmost thoughts and desires, " The Lord searcheth all hearts and understandeth all the thoughts of men'' (Prov. xxviii. 9). By this absolute surrender of self to God man places the proximate condition necessary for grace to become the efficient cause of his sanctification.