Graves would have argued that much of the mythos surrounding Christian [& Islamic] images of Mary echoes a much deeper stratum of beliefs.

A sense of how completely he believed "there is ...one story only" can be found in his "The White Goddess: A Historical Grammar of Poetic Myth." It's an idiosyncratic, encyclopaedic, incoherent & thoroughly ahistorical investigation of mother/goddess imagery in the Old World, much beloved by neo-pagans.

[Below is the poem which graces the intro to that book.]

I can't recommend "The White Goddess" for historical or mythological accuracy - it's a bit of a mess. Graves collapses all the diversity of divine images into an undifferentiated mass, w/ little regard for the psychological & spiritual complexities underlying often wildly different belief systems of varied cultures & times.

All paganisms were the same to him - a deeply condescending view, if one steps back from it a bit. Graves was not completely unaware of this weakness - he complained of having no success in getting useful input for the book from Irish & Welsh scholars, for example, which was all the more ironic in that his father & grandfather were so intimately involved w/ the Celtic Revival & the investigation of Irish antiquities.

OTOH, he did identify some powerful common currents in mythological imagery thru the Old World, & "The White Goddess" is an interesting document from a very important historical moment.

Graves, like so many of his generation, was deeply affected by WWI. Over the yrs, as he struggled to make sense of the senseless, he came to believe that the worst aspects of his time - mechanised mass slaughter, the hideous cult of death that seemed an intrinsic part of "civilised manliness" in the modern era - could be traced to the ancient overthrow of matriarchal principles & values in favour of a warrior worshipping patriarchal system.

He found solace & promise in the image of the all-powerful goddess/mother - tho he had at best very strained relationships with the actual women in his life - & his poetry & prose alike frequently returned to this theme.

He was far from alone in this reaction: the modern anti patriarchal critique of 'mainstream' religions has some of its roots [tho not all] in the struggle to understand how 'civilisation' could generate such unspeakable horrors; so too does Jungian psychology, & the post-Christian revival of European [-based] paganisms.

It's still w/ us, of course, as our own present-day warrior cultists dominate the headlines. Ordinary people still are slaughtered every day in the name of one or another god, or live under the threat of those who imagine themselves engaged in a cosmic battle against 'evil' - & thus entitled to wreak unimaginable evil themselves.

Graves didn't shrink from the everyday cruelties of nature, but his adult life was a continuous rejection of this latter form of insanity.

All saints revile her, and all sober men
Ruled by the God Apollo's golden mean -
In scorn of which we sailed to find her
In distant regions likeliest to hold her
Whom we desired above all things to know,
Sister of the mirage and echo.

It was a virtue not to stay,
To go our headstrong and heroic way
Seeking her out at the volcano's head,
Among pack ice, or where the track had faded
Beyond the cavern of the seven sleepers:
Whose broad high brow was white as any leper's,
Whose eyes were blue, with rowan-berry lips,
With hair curled honey-coloured to white hips.

The sap of Spring in the young wood a-stir
Will celebrate with green the Mother,
And every song-bird shout awhile for her;
But we are gifted, even in November
Rawest of seasons, with so huge a sense
Of her nakedly worn magnificence
We forget cruelty and past betrayal,
Heedless of where the next bright bolt may fall.