If we look critically at human life with rational insight, it turns out to be threefold—spiritual life, moral life, and civic life. These lives are distinguishable: some people live a civic life but not a moral or spiritual one, some live a moral life but not a spiritual one, and some live a civic and a moral life and a spiritual life as well. These last are the ones who are leading heaven’s life, while the former are leading the world’s life, divorced from heaven’s life.
To begin with, then, we may gather that a spiritual life is not separate from a natural life or the world’s life but is united to it like a soul to its body; and if they were separated, it would be like a house without a foundation, as just stated.
In fact, moral and civic living is what spiritual life does, for intending well is the essence of spiritual life and behaving well is the essence of moral and civic life. If these are separated from each other, spiritual life consists solely of thinking and talking, and the intent ebbs away because it has no support. Yet intent is our actual spiritual substance.
from Heaven and Hell, Section 529