Selection from Arcana Coelestia ~ Emanuel Swedenborg
As the correspondence of diseases is to be treated of, be it known that all diseases in man have correspondence with the spiritual world; for whatever in universal nature has not correspondence with the spiritual world cannot exist, having no cause from which to exist, consequently from which to subsist. The things that are in nature are nothing but effects; their causes are in the spiritual world, and the causes of these causes, which are ends, are in the interior heaven. Nor can the effect subsist unless the cause is constantly in it, because the effect ceases when the cause ceases. Regarded in itself the effect is nothing else than the cause, but so clothed outwardly as to enable the cause to act as a cause in a lower sphere.Similar to the relation of the effect to the cause is that between the cause and the end; unless a cause also exists from its cause, which is an end, it is not a cause; for a cause without an end is a cause in no order, and where there is no order nothing is effected.
From this it is now plain that regarded in itself an effect is a cause, and that regarded in itself a cause is an end, and that an end of good is in heaven and proceeds from the Lord; consequently that an effect is not an effect unless a cause is in it, and constantly in it; and that a cause is not a cause unless an end is in it, and constantly in it; and that an end is not an end of good unless the Divine which proceeds from the Lord is in it. Hence it is also plain that as each and all things in the world have come forth from the Divine, they continue to come forth from the Divine
These things have been said in order that it may be known that diseases also have correspondence with the spiritual world; not a correspondence with heaven, which is the Grand Man, but with those who are in what is opposite, thus with those who are in the hells.
By the spiritual world in the universal sense is meant both heaven and hell; for when man dies he passes out of the natural into the spiritual world.That diseases have correspondence with such is because they correspond to the cupidities and passions [desires and cravings] of the lower mind, which are also their origins;
for the origins of diseases are, in general, intemperance, luxury of various kinds, mere bodily pleasures, as also feelings of envy, hatred, revenge, lewdness, and the like, which destroy man's interiors;and when these are destroyed the exteriors suffer, and drag man into disease, and so into death. It is known in the church that the death of man is from evils, or on account of sin; and it is the same with diseases, for these belong to death.
From all this it is evident that even diseases have correspondence with the spiritual world, but with unclean things there; for diseases are in themselves unclean, because as before said they spring from unclean things.
All the infernals induce diseases, but with a difference, for the reason that all the hells are in the desires and lusts of evil, and thus are contrary to the things of heaven; wherefore they act upon man from what is opposite.
Heaven, which is the Grand Man, holds all things together in connection and safety; hell, being in what is opposite, destroys and severs all things.Consequently if the infernals are applied, they induce diseases and at last death. Yet they are not permitted to flow as far as into the solid parts of the body, or into the parts of which man's viscera, organs, and members consist, but merely into his cupidities and falsities.
It is only when the man falls into disease that they flow into such unclean things as belong to the disease; for as before said nothing ever takes place in man without a cause in the spiritual world.If the natural with man were separated from the spiritual, it would be separated from all cause of existence, and thus from all that is vital.
Yet this does not hinder man's being healed in a natural way; for the Lord's providence concurs with such means.That this is so has been given me to know by much experience, and this so often and for so long that no doubt was left; for evil spirits from such places have been applied to me often and long, and according to their presence they induced pains, and also diseases. I was shown where they were, and what they were, and was told also where they came from.
(from Arcana Coelestia 5711-5713)