This, then, is the balance between heaven and hell. People in the world of spirits are in this balance, since the world of spirits is halfway between heaven and hell. So too we in the world are kept in the same kind of balance, since the Lord governs us in the world by means of spirits in the world of spirits, a subject I shall deal with below in a separate chapter.
This kind of balance would not be possible unless the Lord ruled both heaven and hell and regulated both. Otherwise, malicious falsity would cross the boundaries and affect the simple, good people who are in the outmost parts of heaven, people who are more easily misled than actual angels. This would destroy the balance, and with the balance would go our freedom.
Like heaven, hell is differentiated into communities. In fact, there are just as many communities in hell as there are in heaven, since each heavenly community has an opposite number in hell, for the sake of the balance.
However, the communities in hell are differentiated according to their evils and consequent falsities because the communities in heaven are differentiated according to their good will and consequent truths. We may be sure that there is some evil opposite to everything good and some falsity opposite to everything true from the fact that nothing exists without a relationship to its opposite. The opposite enables us to know its actual nature and level. Opposition is the source of all perception and sensation.
This is why the Lord is constantly taking care that every community of heaven has its opposite in some community of hell and that there is a balance between them.
from Heaven and Hell, Section 540-541