413. (13) Wisdom or the understanding, from the potency given to it by love, can be elevated and can receive such things as are of light out of heaven, and perceive them. That man has the ability to perceive arcana of wisdom when he hears them, has been shown above in many places. This capacity of man is called rationality. It belongs to every man by creation. It is the capacity to understand things interiorly, and to decide what is just and right, and what is good and true; and by it man is distinguished from beasts. This, then, is what is meant when it is said, that the understanding can be elevated and receive things that are of light out of heaven, and perceive them. That this is so can also be seen in a kind of image in the lungs, for the reason that the lungs correspond to the understanding. In the lungs it can be seen from their cellular substance, which consists of bronchial tubes continued down to the minutest air-cells, which are receptacles of air in respirations; these are what the thoughts make one with by correspondence. This cell-like substance is such that it can be expanded and contracted in a twofold mode, in one mode with the heart, in the other almost separate from the heart. In the former, it is expanded and contracted through the pulmonary arteries and veins, which are from the heart alone; in the latter, through the bronchial arteries and veins, which are from the vena cava and aorta, and these vessels are outside of the heart. This takes place in the lungs for the reason that the understanding is capable of being raised above its proper love, which corresponds to the heart, and to receive light from heaven. Still, when the understanding is raised above its proper love, it does not withdraw from it, but derives from it what is called the affection for knowing and understanding, with a view to somewhat of honor, glory, or gain in the world; this clings to every love as a surface, and by it the love shines on the surface; but with the wise, the love shines through. These things respecting the lungs are brought forward to prove that the understanding can be elevated and can receive and perceive things that are of the light of heaven; for the correspondence is plenary. To see from correspondence is to see the lungs from the understanding, and the understanding from the lungs, and thus from both together to perceive proof.