pure cinema

Hello all, just thinking about our avante garde friends and their attempts to create 'pure cinema' and wondering if such a thing as 'pure cinema' is possible and if so what could it possibly be and also why the preoccupation with purity in the first place??
Old mate Clement Greenberg writes: "It quickly emerged that the unique and proper area of competence of each art coincided with all that was unique to the nature of its medium".  Clement goes on for some time but basically what he's getting at is that each art practice is unique in one particular domain, i.e. the medium succeeds where no other medium can, and whats more it is the medium itself  that defines this uniqueness.  Clement states that paintings unique quality is that it is flat.  I am somewhat perplexed by this claim as photography and film exist on a flat surface and can you not paint a sculpture and call it a painting?  Can someone please help me with this?  Nonetheless I am a little intrigued by the idea that each medium has a quality that is unique to itself.  What could it be for film?  The cut perhaps, that is quite unique and integral to the film medium.  Could it be the multi layered culmination and integration of the visual image, music and narrative?  This too is unique to film.
If we consider either of these characteristics as the defining factors, the idea of pure cinema seems idiotic, imagine 'the pure cut' or 'the pure montage'.  It's downright silly.  Can cinema be 'pure'?  Is this an idea for wankers?
It seems to me that the idea of purity with relation to 'art' is all tied up with ideas of the spirit.  The spirit is expressed through 'pure' artistic expression.  Such expression is realised through a spontaneous outpouring of inspiration that is unhindered by the ego blah blah blah.  If my little suspicion is correct I do wonder how film could ever hope to be 'pure' as it relies so heavily on planning, orgainisation and collaboration?