As regards the conjunction itself, it is this which effects man's regeneration; for man is regenerated by the fact that the truths in him are being conjoined with good, that is, that the things which belong to faith are being conjoined with those which belong to charity.
The Lord is indeed the subject treated of how He made His natural Divine, consequently how He united Divine good to the truth in His natural. But as man's regeneration is an image of the Lord's glorification, this regeneration is also treated of at the same time in the internal sense. And as regeneration can fall into man's idea, but not so fully the Lord's glorification, the latter may be illustrated by the former.
The conjunction of good with truths (by which regeneration is effected) progresses more and more interiorly, that is, truths are successively conjoined more interiorly with good. For the end of regeneration is that the internal man may be conjoined with the external, thus the spiritual with the natural through the rational. Without the conjunction of both of these, there is no regeneration. Nor can this conjunction be effected until good has first been conjoined with truths in the natural; for the natural must be the plane, and the things that are in the natural must correspond. This is the reason why when the natural is being regenerated, the conjunction of good with truths becomes successively more interior. For the spiritual conjoins itself first with the things which are inmost in the natural, and then by means of these with those which are more exterior. Nor can man's internal conjoin itself with his external, unless the truth in the external becomes the good of truth, that is, truth in will and act.
From the Scripture:
Where "Jacob" is spoken of, the subject treated of in the internal sense was the acquisition of truth in the natural, which acquisition is made in order that this truth may be conjoined with good, for all truth is for the sake of this end. "Jacob," in the internal sense, is this truth, and "Esau" is the good with which the truth is to be conjoined. Before the conjunction is effected, truth appears to be in the first place; but after the conjunction, good is actually in the first place. This is also what is signified by the prophecy of Isaac to Esau:
"Upon thy sword shalt thou live, and thou shalt serve thy brother; and it shall come to pass when thou shalt have the dominion, that thou shall break his yoke from off thy neck" (Gen. 27:40).
And this state is what is described in the present chapter. For this reason Jacob calls Esau his "lord," and himself his "servant"
Be it known that Jacob here represents the good of truth. But regarded in itself the good of truth is only truth; for so long as truth is in the memory only, it is called truth; but when in the will and thence in act, it is called the good of truth; for to do truth is nothing else. Whatever proceeds from the will is called good, for the essential of the will is love and the derivative affection; and everything that is done from love and its affection is named good. Neither can truth be conjoined with the good that flows in through the internal man and is in its origin Divine (which is here represented by Esau), until the truth is truth in will and act; that is, the good of truth. For the good that flows in through the internal man and is in its origin Divine, flows into the will, and there meets the good of truth that has been instilled through the external man. (AC 4337)
for then for the first time they can be conjoined, inasmuch as the Lord flows in with man through his internal man, and in fact through the good therein. This good can be conjoined with good in the external man, but not good with truth immediately.
From this it may be seen that the truth in man must first become truth in will and act (that is, the good of truth), before the conjunction of the rational with the natural, or the internal man with the external, can take place. But how truth becomes the good of truth, must be evident to everyone who pays attention.
All Divine truth regards these two precepts - to love God above all things, and the neighbor as one's self. It is these precepts from which and for the sake of which truths are, and to which truths tend, more nearly and more remotely. Therefore when truths are put into act, they are instilled successively into their beginning and their end, namely, into charity toward the neighbor, and into love to the Lord; and thereby truth becomes good, which is called the good of truth; and when this takes place, it can then be conjoined with the internal man, which conjunction becomes successively more interior, in proportion as more interior truths are implanted in this good.
Act precedes, man's willing follows; for that which a man does from the understanding, he at last does from the will, and finally puts it on as a habit; and it is then instilled in his rational or internal man.
And when it has been instilled in this, the man no longer does good from truth, but from good; for he then begins to perceive therein somewhat of blessedness, and as it were somewhat of heaven. This remains with him after death, and by means of it he is uplifted into heaven by the Lord.
(from Arcana Coelestia 4353)