God is the ultimate other.
The full embodiment of how we see ourselves from the perspective of others.
Society is our imagined audience, as we act in our daily lives.
But our imagined audience is different throughout our day. And in private life, we can sometimes partake in actions with no audience.
When we reflect on our private actions, we do so from a more God-like perspective. Imaging all the moral judgements that could be made about us, with no particular person or persons in mind.
God is the totality of expectations, "morality," laid upon us by those around us.