The understanding in a man can be elevated into the light, that is, into the wisdom in which the angels of heaven are, according to the cultivation of his reason; and in like manner his will can be elevated into the heat of heaven, that is, into love, according to the deeds of his life; but the love of the will is not elevated except so far as the man wills and does those things which the wisdom of the understanding teaches.
By the human mind are meant its two faculties, which are called the understanding and the will. The understanding is the receptacle of the light of heaven, which in its essence is wisdom, and the will is the receptacle of the heat of heaven, which in its essence is love, as was shown above. These two, wisdom and love, proceed from the Lord, as a sun, and flow into heaven universally and particularly, whence the angels have wisdom and love; and they also flow into this world universally and particularly, whence men have wisdom and love.  But these two united proceed from the Lord, and likewise united flow into the souls of angels and men, but they are not received united in their minds. Light which makes the understanding is first received there, and love which constitutes the will is received gradually. This also is of providence, because every man is to be created anew, that is, reformed, and this is effected through the understanding; for from infancy he must acquire the knowledges of truth and good, which will teach him to live well, that is, to will and act rightly. Thus the will is formed through the understanding.  For the sake of this end, there is given to man the faculty of elevating his understanding almost into the light in which the angels of heaven are, that he may see what he ought to will and thence to do, in order that he may be prosperous in the world for a time, and be happy after death to eternity. He becomes prosperous and happy if he procures for himself wisdom, and keeps his will under obedience to it; but unprosperous and unhappy if he subjects his understanding under obedience to his will. The reason is, because the will from birth inclines to evils, even to enormous ones; wherefore unless it were curbed by the understanding, a man would rush into heinous things, yea, from his inborn savage nature, he would depopulate and slaughter for the sake of himself all those who do not favor and indulge him.  Furthermore, unless the understanding could be separately perfected, and the will by means of it, a man would not be a man, but a beast. For without that separation, and without the ascent of the understanding above the will, he would not be able to think, and from thought to speak, but only to express his affection by sounds; neither would he be able to act from reason, but only from instinct; still less would he be able to know the things which are of God, and God by means of them, and thus to be conjoined to Him, and to live to eternity. For a man thinks and wills as from himself, and this as from himself is the reciprocal of conjunction; for there cannot be conjunction without a reciprocal, just as there cannot be conjunction of the active with the passive without reaction. God alone acts, and man suffers himself to be acted on, and he reacts in all appearance as from himself, though interiorly it is from God.  From these things rightly perceived it may be seen what is the quality of the love of a man's will if it is elevated by means of the understanding, and what is its quality if it is not elevated; consequently, what is the quality of the man. But this quality of a man if the love of his will is not elevated by means of the understanding shall be illustrated by comparisons. He is like an eagle which flies on high, and as soon as it sees the food below which is the object of its desire, as chickens, young swans, yea, young lambs, swoops down in a moment and devours them. He is also like an adulterer, who conceals a harlot in a cellar below, and by turns goes up to the highest part of the house, and talks wisely with those who dwell there about chastity, and by turns hastens away from his companions, and indulges his lasciviousness below with his harlot.  He is also like a thief on a tower, who there pretends to keep watch, but who, as soon as he sees an object of plunder below, hastens down and seizes it. He may also be compared to marsh-flies, which fly in a column over the head of a running horse, but which fall down when the horse stops, and immerse themselves in their marsh. Such is the man whose will or love is not elevated by means of the understanding, for he then stands still below at the foot, immersed in the unclean things of nature and the lusts of the senses. It is altogether otherwise with those who subdue the allurements of the cupidities of the will by means of the wisdom of the understanding. With these the understanding afterwards enters into a conjugial covenant with the will, thence wisdom with love, and they dwell together above with delights.