15. That a man who is not spiritual can yet think rationally and speak from that thought, like a spiritual man, is because man's understanding can be uplifted into the light of heaven, which is truth, and can see from it; but his will cannot be in the same way uplifted into the heat of heaven, which is love, so as to act from that heat. It is for this reason that truth and love do not make a one in a man unless he is spiritual. And it is for this reason also that man can speak; and it is this which makes the difference between a man and a beast. It is by means of this capacity of the understanding to be uplifted into heaven when as yet the will is not so uplifted, that it is possible for a man to be reformed and to become spiritual; but he does not begin to be reformed and become spiritual until his will also is uplifted. It is from this superior endowment of the understanding over the will, that a man, of whatever character he may be, even if evil, is able to think and therefore to speak rationally, as if he were spiritual. That still in spite of this he is not rational, is because the understanding does not lead the will, but the will leads the understanding. The understanding merely teaches and shows the way, as has been said in the Doctrine of the Holy Scripture (n. 115). And so long as the will is not in heaven together with the understanding, the man is not spiritual, and consequently is not rational; for when he is left to his will or love, he throws off the rational things of his understanding respecting God, heaven, and eternal life, and adopts in their stead such things as are in agreement with his will's love, and these he calls rational. But these matters shall be elucidated in the treatises on Angelic Wisdom.