Mary and Isis are often shown sitting, with their laps then becoming thrones for god (the god Horus, the god Jesus).  Mary & Isis are thus the Source of the God's very rulership.  The subtle Source of divinity itself. 
The word “source” is actually the first word of the entire Bible, In the Beginning.  And once again is a feminine word in the original Hebrew. In the beginning is really B'rashith, meaning, “Source,” and some Hebrew scholars translate as “womb”. 
So instead of, “In the Beginning,” you could say - "In the source," or "In the womb" the Elohim filled the heavens and the earth. The word “created” in the first sentence of the Bible is actually “filled”. Elohim filled the heavens and the earth like filling a womb.

Sometimes we see Mother Mary and we suspect it is Magdalene, other times it's really Sophia. Mother Mary was the only form of the feminine Divine allowed, so painters had to camouflage the other Christian goddesses as her.
The clues are easy to find once you know the code. 

Mosaic in the Hagia Sophia,

Constantinople/Istanbul     9th Century