Rational individuals can understand what has been said so far because they can see this from the chain of causes and from truths in their pattern. However, people who are not rational do not understand these things. There are several reasons why they do not understand. The primary one is that they do not want to understand because these things contradict the false opinions that they have made their truths. People who do not want to understand for this reason close off the path of heaven into their rational ability. Even so, it can still be opened if only their will does not offer resistance (see Section 424). A great deal of experience has shown me that people can understand what is true and be rational if only they are willing. Quite often, evil spirits who have become irrational by denying the Divine and the truths of the church in this world (and convincing themselves in their denial) have by divine compulsion been faced toward people who were in the light of truth. Then they understood everything like angels and admitted that they were true and that they understood everything. However, the moment they turned back toward the love proper to their own intentions, they did not understand anything and said just the opposite.
I have even heard some hellish people saying that they knew and recognized that what they were doing was evil and what they were thinking was false, but that they could not resist the gratification of their love and therefore of their will. This moved their thoughts to see evil as good and falsity as true. I could see from this that people who are immersed in false notions because of their malice could understand and could therefore be rational, but that they did not want to. The reason they did not want to was that they loved false notions more than true ones because the former supported the evil pursuits they were engaged in. Loving and intending are the same thing because we love what we intend and intend what we love.
Since we are by nature able to understand what is true if we are willing to, I have been granted the privilege of supporting spiritual truths, truths of the church and heaven, by rational considerations. This is to the end that the false notions that have obscured the rational functioning of many people may be dispelled by rational considerations and their eyes perhaps opened a little. If people are focused on truths, it is granted them to support spiritual truths by rational ones. Who would possibly understand the Word simply from its literal meaning unless they saw some truths in it by enlightened reason? What else is the cause of the many heresies drawn from the same Word?
from Heaven and Hell, Section 455