hought produces respiration; it is evident,
also, that affection, which is of love, produces thought, for thought
without affection is precisely like respiration without a heart, a thing
impossible. From this it is clear that affection, which is of love,
conjoins itself to thought, which is of the understanding (as was said
above), in like manner as the heart does in the lungs.

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