One aspect of thought which I find difficult is that there seem to be two ideas – that of unity, or oneness, and that of duality, or twoness – which seem equally primordial and basic. It seems they may be solved this way. God – Who is one – is infinite; but so long as He is conceived ontologically and cataphatically, as the Creator-as-distinguished-from-Creation, He is not everything. He is Being, but there is also non-Being, and hence the possibility of freedom, creation, and spontaneity; though He is perfect and immutable, He is not static. Being and non-Being dialectically reconcile in Becoming, yet within the idea of Being is already contained the idea of non-Being, so Becoming does not proceed externally from Being automatically in an emanationist sense; nor do the dialects proceed by means of conflict or strife. Non-Being is not supposed to be evil, but rather than potential for Being and a part of God’s act of Creation; hence the primal idea of duality would not have been lost if Satan had never fallen. It is unnecessary that “non-being” and darkness (or night) has become evil.
We cannot of course posit an absolute duality between Being and Non-Being, though, nor can in an ultimate way delimit God to be a part of reality, as reality minus Creation, as Creator separated from Creation. God's "withdrawing" from the world, creating an apparent space for the world to exist outside of Himself - tzimtzun as the Kabbalah calls it - is a matter of God's relation to us - God as He exists energetically - not God as He exists in and of Himself, God in His essence. As it does not pertain to the ineffable Essence of God, His tzimtzun is a divine illusion, or maya, by which the infinite and boundless God - Reality itself - appears to be one part of the sum of reality, rather than the whole, or appears to give space for reality "outside" Himself.
The orthodox theologian knows, of course, that God is immanent in His transcendence, that He is "closer to man than his jugular vein", and that it would be more correct to say (with Aquinas) that the world is in God, than that God is in the world. Non-Being - the space in which the universe is created - is nothing other than God. We were created and subsist in Him. One cannot posit duality between Being and Non-Being - though while preserving their nonduality, one must acknowledge a conceptual difference (a difference found in our human minds) between the ineffable depths of divine darkness, and the maya in divinis in which the universe is created.
Christian orthodoxy has often favored dualistic language - as every Christian creed begins, "I believe in God, the Father almighty, Creator of Heaven and earth." This should not be a problem for nondual Christianity. A true nondualism overcomes the duality between dualism and nonduality, so that the gnostic should be equally comfortable with dualistic or nondualistic language. They are not two truths, after all, or conflicting models, but rather two insights into the mystery of God and the world.