This brief reflection is based on the explanation of the phrase: Possession in oneness and not loss in oneness
The full Sri Aurobindo’s passage is:
Possession in oneness and not loss in oneness is the secret. God and Man, World and Beyond-world become one when they know each other. Their division is the cause of ignorance as ignorance is the cause of suffering.
Thoughts and Glimpses, CWSA 13: 202-203
with the Mother’s commentary:
According to what Sri Aurobindo says here, the reality of the universe is what is called God or godhead, but essentially it is Delight. The universe is created in Delight and for Delight. But this Delight can exist only in the perfect oneness of the creation with its creator, and Sri Aurobindo describes this oneness as the Possessor—that is, the Creator—the Possessor being possessed by his creation, a sort of reciprocal possession which is the very essence of the Oneness and the source of all delight.
And it is because of division—because the Possessor no longer possesses and because the possessed no longer possesses the Possessor, division is created and the essential Delight is changed into ignorance, and this ignorance is the cause of all suffering. “Ignorance”, not in the sense in which it is usually 8understood, for that is what Sri Aurobindo calls Nescience: that ignorance is a consequence of the other. True ignorance is ignorance of the oneness, the union, the identity. And that is the cause of all suffering.
9 January 1957, CWM 09: 8 – 9