The spirits who are with us—both those united to heaven and those united to hell—never flow into us from their own memory and consequent thought. If they did flow into us from their own thought it would seem to us exactly as though their character was our own (see above, Section 256). However, there does flow into us through them an affection from a love of what is good and true from heaven and an affection from a love of what is evil and false from hell. So to the extent that our own affection agrees with what is flowing in, we accept its influence in our thinking. This is because our more inward thought is in complete accord with our affection or love. To the extent that our own affection does not agree, we do not accept [the influence].
We can see from this that thoughts are not instilled into us by spirits but only an affection for what is good or an affection for what is evil. This gives us a choice because it gives us freedom. It means that in our thought we can accept what is good and reject what is evil, since we know from the Word what is good and what is evil. What we accept in thought from affection becomes part of us, while what we do not accept in thought from affection does not become part of us. This enables us to determine the nature of the inflow into us of the good from heaven and of the evil from hell.
I have been enabled to learn where we get the anxiety, distress of mind, and inward sadness called depression. There are spirits who are not yet united with hell because they are still in their first state (which will be described later when we talk about the world of spirits). They love half-digested and noxious substances like the foods that are becoming excrement in the stomach, so they attach themselves to the same sort of matter in us, because they find delight in it; and they talk with each other there out of their evil affection. The emotional tone of their conversation flows into us, and since it is contrary to our affection, it brings about a sadness and an anxious depression; while if it agrees with our affection, it brings about a sense of happiness and exhilaration. These spirits can be seen in the neighborhood of the stomach, some on the left and some on the right, some lower and some higher, nearer or farther away—variously depending on the affections they are involved in.
A great deal of experience has convinced me that they are the source of our anxiety of spirit. I have seen them, heard them, felt the anxieties that well up from them. I have talked with them, they have been driven off and the anxiety has ceased, they have come back and the anxiety has returned, I have observed its increase and decrease as they drew near and moved away. It has become clear to me, then, where that anxiety originates that is blamed on a stomachache by people who do not know what conscience is because they do not have any.
from Heaven and Hell, Sections 298, 299
Section 256: Published 3/3/2017