According to the Doctrine of Unity, God or the One communicates to Creation through an entity called the Kamil or the Entelechy. Kamil is present in all sentient beings, and so in order to achieve unity with the One, humans must strive to achieve unity with one another. They identify this principle with the strict monotheism of Islam, which demands total submission to the will of God.
On the Night of Fana, when the Batini were first formed, the Khwaja al-Akhbar manifested in a moment of perfect Unity: not only the minds of the mages present but the physical space they inhabited collapsed into one point. It is from this moment of revelation that the Doctrine of Unity was developed.
Even those Choristers who subscribe to polytheistic faiths tend to posit the existence of the One, a transcendent cosmic entity of whom everything is a shard.
Gnosticism and Qabbalism
Both the Order of Hermes and the Solificati are influenced by a combination of Gnosticism, a Christian heresy from the early centuries of the Common Era, and Qabbalism, an ancient Jewish mystic tradition. The Gnostic Creator, equated to Keter in the Qabbalah's Tree of Life, is the One from whom all other concepts emanate; by getting back to first principles mages can achieve unity with the One and shed the burden of corrupted material form.