I was blown away the first time I read this in the Introduction of Jacob Milgrom's Commentary on Leviticus:

"The basic premises of pagan religion are (1) that its deities are themselves dependent on and influenced by a metadivine realm, (2) that this realm spawns a multitude of malevolent and benevolent entitites, and (3) that if humans can tap into this realm they can acquire the magical power to coerce the gods to do their will. The eminent Assyriologist W.G. Lambert has stated, 'The impression is gained that everyday religion [in Mesopotamia] was dominated by fear of evil powers and black magic rather than a positive worship of the gods ... the world was conceived to be full of evil demons who might cause trouble in any sphere of life. If they had attacked, the right ritual should effect the cure ... Humans, as well as devils, might work evil against a person by the black arts, and here too the appropriate ritual was required.'

The Priestly theology [of Leviticus] negates these premises. It posits the existence of one supreme God who contends neither with a higher realm nor with competing peers. The world of demons is abolished; there is no struggle with autonomous foes, because there are none. With the demise of the demons, only one creature remains with 'demonic' power--the human being. Endowed with free will, human power is greater than any attributed to humans by pagan society. No only can one defy God but, in Priestly [Levitical] imagery, one can drive God out of his sancturary. In this respect, humans have replaced demons. ... Humans can drive God out of the sancturary by polluting it with their moral and ritual sins. All that the priests can do is periodically purge the sanctuary of its impurities and influence the people to atone for their wrongs. ... The sanctuary symbolized the presence of God; impurity represented the wrongdoing of persons. If persons unremittingly polluted the sanctuary, they force God out of his sanctuary and out of their lives.

... The sanctuary stands in need of constant purification lest it be abandoned by its resident god. But whereas the pagans hold that the source of impurity is demonic, Israel, having expunged the demons from its beliefs, attributes impurity to the rebellious and inadvertent sins of humans instead."