7812. In addition to the spirits who have just been mentioned there are also spirits who urge things that are contrary. They are those who when they lived in the world were banished from association with others because they were evil. When they arrive they look like fire moving through the air, which comes down close to one's face. They place themselves low down at a person's hinder parts, and from there they direct what they say to the upper parts. They make statements that contradict things said by an instructor spirit under the direction of the angels; that is, they declare that the person does not need to conduct his life in accordance with that instruction, but to follow his own inclination and desire, and similar ideas. Usually these spirits arrive immediately after the first ones have departed. But people there know exactly who these spirits are and what they are like, and therefore do not worry about them. All the same, they learn in this way what evil is, and so what good is; for one learns from evil what good is, indeed one knows the nature of good from its opposite, to be exact. Every perception of something is arrived at by relating it to, and reflecting on its differences from, things that are contrary to it in varying ways and degrees.