18. The reason everyone must be engaged in what is good and what is true together after death or in what is evil and what is false is that good and evil cannot be united. Neither can good and any falsity that is prompted by evil, or evil and any truth that is prompted by anything good. Such things are opposites, and opposites battle with each other until one destroys the other.

It is people who are engaged in evil and good at the same time that are referred to in these words of the Lord to the church in Laodicea in the Book of Revelation:

I know your works, that you are neither cold nor hot. I wish that you were either cold or hot. However, since you are lukewarm and neither cold nor hot, I am about to spit you out of my mouth (Revelation 3:15-16),

and by these words of the Lord:

No one can serve two masters. You will either hate one and love the other or cling to one and ignore the other. (Matthew 6:24)