I know many esotericists maintain that theism is at a lower level, spiritually speaking, than non-dualism or monism and that love of God is dualistic and therefore outside the absolute. Setting aside the fact that they often reduce love of God to bhakti which is more like devotionalism, I see this as the typical metaphysical error of the intellectually inclined and have written a lot on the subject - see the non-duality topic on the right of this page. I will not go fully into the whys and wherefores of this here but, briefly, my position is that in a truly non-dualistic world there would be no need for creation or manifestation if you prefer to call it that. If being is the end of it all then why become? That makes no sense. But it does make sense if the fundamental reality of the universe is a Who not a What and if spirit, the absolute, is enriched by matter or the relative. Mixing in multiplicity with unity brings about a universe that is not just unchanging life but creative, dynamic, active, ever self-renewing and transcending, and also one in which there are many beings which allows for love as opposed to impersonal compassion which is the best you can hope for under non-duality. In such a universe you still have all the truth of spirit but you also have quality (impossible in pure oneness) which gives rise to the good and the beautiful as well as the true. Spirit and matter, being and becoming, life and its expression, are more than just spirit alone. When the two are joined in what we can justifiably call holy matrimony, you have something far greater than simple universal oneness. In this scenario the individual is not seen as the stain on spiritual life as is the case in non-dualism but the whole point of spiritual life. United with God, it (he or she really) becomes the fulfillment of being.
Does eternity simply annihilate time or does time add something to eternity? For non-dualistic philosophies time is an illusion that is dispelled when eternity is known, if, that is, they are faithful to their fundamental premise. The same is true in the case of the individual. God plus Man can be no more than God alone. Such, in my view, are the perils of abstract thinking. In fact, time does add something to eternity and Man does add something to God. Why else would God have created or why is there something rather than nothing if you wish to look at it in philosophical terms? Even if you say God created because of love that is still adding something. Moreover, do you love what is not real? If God loves Man then Man is real and not something swallowed up in oneness as though he had never been and brought nothing to the table. And if you say that God the Creator came out of Universal Being and is a step down from that exalted state, I would ask how such a thing might have come about? Something cannot come from nothing and all effects must exist in their causes. The name of God is I AM. Abstract being is an invention of the philosophers and though mystical states of oneness certainly exist and can be experienced these correspond to divine immanence, God in us, and do not detract from his transcendent selfhood, the real ultimate reality.