The angelic heavens may serve as an example for better comprehension of the reality and nature of distinct levels and of how they differ from gradual levels. There are three heavens marked off by vertical levels so that one is underneath another. The only way they communicate is by an inflow that comes from the Lord through the heavens in sequence down to the lowest, and not the other way around.
Each heaven on its own, though, is marked off not by vertical levels but by horizontal ones. The people in the middle or center are in the light of wisdom, while those around them all the way to the borders are in the shadow of wisdom. That is, wisdom wanes all the way to ignorance as the light declines into shadow, which happens gradually.
It is the same with us. The inner realms of our minds are marked off into as many levels as are the angelic heavens, with one level over another. So the inner realms of our minds are marked off in distinct or vertical levels. This is why we can be engaged in the lowest level, a higher level, or the highest level depending on the level of our wisdom. It is why the higher level is closed when we are exclusively engaged in the lowest one, and why the higher one is opened as we accept wisdom from the Lord. There are also gradual or horizontal levels in us just as there are in heaven.
The reason we resemble the heavens is that we are miniature heavens as to the deeper realms of our minds when we are engaged in love and wisdom from the Lord. (On our being miniature heavens as to the deeper realms of our minds, see Heaven and Hell 51–58.)
from Divine Love and Wisdom, Section 186