24. The Lord provides for the union of what is good and what is true by comparison. We recognize the quality of what is good only by its relationship to something that is less good and by its opposition to what is evil. This is the source of everything in us that is perceptive and sensitive, because this is what gives perception and sensitivity their quality. That is, anything pleasing is perceived and sensed by contrast with something that is less pleasing and by what is unpleasant, anything beautiful by something less beautiful and by something ugly. By the same token, any good that love does is perceived and sensed by contrast with what is less good and by something evil, and anything true that wisdom offers is perceived and sensed by contrast with what is less true and by something false.

There need to be differences in everything, whether great or small; and when these differences create a balanced opposition between the great and the small, then there is a comparison between the levels in each direction. As a result, our perception and sensation are either enhanced or dulled.

We need to realize, that is, that the opposition may either deaden or intensify our perceptions and sensations. It deadens them when the opposites are mingled and intensifies them when they are not mingled. This is why the Lord separates goodness from evil very precisely so that they will not be mingled in us, just as he keeps heaven and hell separate.