People can realize that non-Christians as well as Christians are saved if they know what constitutes heaven in us; for heaven is within us, and people who have heaven within them come into heaven. The heaven within us is our acknowledgment of the Divine and our being led by the Divine. The beginning and foundation of every religion is its acknowledgment of the Divine Being; a religion that does not acknowledge the Divine Being is not a religion at all. The precepts of every religion focus on worship, that is, on how the Divine is to be honored so that we will be acceptable in its sight; and when this fully occupies the mind (or, to the extent that we intend this or love this) we are being led by the Lord.
It is recognized that non-Christians live lives that are just as moral as the lives of Christians—many of them, in fact, live more moral lives. A moral life may be lived either to satisfy the Divine or to satisfy people in this world. A moral life that is lived to satisfy the Divine is a spiritual life. The two look alike in outward form, but inwardly they are totally different. One saves us, the other does not. This is because if we live a moral life to satisfy the Divine we are being led by the Divine; while if we live a moral life to satisfy people in this world, we are being led by ourselves.
This may be illustrated by an example. If we do not do harm to our neighbor because that is against our religion and therefore against the Divine, our refraining from evil stems from a spiritual source. But if we refrain from doing harm to others simply because we are afraid of the law or of losing our reputation or respect or profit—for the sake of self and the world, that is—then this stems from a natural source and we are being led by ourselves. This latter life is natural, while the former is spiritual. If our moral life is spiritual, we have heaven within ourselves; but if our moral life is merely natural, we do not have heaven within ourselves. This is because heaven flows in from above, opens our deeper natures, and flows through those deeper natures into our more outward natures; while the world flows in from below and opens our more outward natures but not our deeper natures. No inflow occurs from the natural world into the spiritual, only from the spiritual world into the natural; so if heaven is not accepted at the same time, the deeper levels are closed. We can see from this who accept heaven into themselves and who do not.
However, the heaven in one individual is not the same as the heaven in another. It differs in each according to the affection for what is good and true. If people are absorbed in an affection for what is good for the sake of the Divine, they love divine truth because the good and the true love each other and want to be united. Consequently, non-Christian people who have not had access to genuine truths in the world still accept them in the other life because of their love.
from Heaven and Hell, Section 319