A hundred years before the birth of Christ, the Greek writer Diodorus Siculus wrote of an island far to the north of the Mediterranean world.
Drawing on now-lost accounts which were hundreds of years older still, he described this island with a "mild climate" which lay "beyond the domain of the Celts".
Here, he claimed, was the birthplace of Leto, mother of the sun god Apollo. For this reason, he wrote, the sun god was venerated there in a "splendid enclosure" which contained a round temple. His account hints at a cult of rebirth involving the sun, the sky and the wind in a mythic ritual of impregnation and regeneration.
Diodorus's account may have nothing whatsoever to do with Ireland and Newgrange. But it just might be a translation into the terms of Greek myth of what were even then ancient rumours of the great round temple that is penetrated by the sun during the winter solstice, giving birth to a new year and renewed life. Since the sacred complex at the Boyne Valley was as ancient in Greek times as the ancient Greeks are to us, it is not at all fanciful to think that some knowledge of its cults and power had made its way into the classical cultures of the Mediterranean.
Move forward 2,000 years and there is another extraordinary testimony to the radiant potency of the culture whose holy places stretched between the Boyne Valley and Tara. Everyone now knows about the sun's entrance into the Newgrange tomb.
But when the site was being excavated in the 1950s and early 1960s, there was no reason to suspect such a thing. The occurrence is unique to the place, and the aperture which allows the light to enter had been hidden for at least a thousand years. Yet the archaeologists who were conducting the excavation were told by locals that some such phenomenon was connected with the mound. A vague but truthful memory had lingered over generations.
Does any of this matter? Not in the straightforward, simple sense that getting to work and earning a living and coping with the stress of contemporary life matters. It doesn't put food on the table or money in the bank.
But in a broader sense, it is important. Some kind of respect for the wonder and fragility of human survival has become almost as necessary to us as food and shelter. We can no longer take our species for granted and we need to be reminded of that fact or else risk extinction.
And it matters in a more local way, too. A society that has changed as rapidly as ours and that has such an awkward and unresolved relationship to its history needs to be reminded that the past is both long and deep and that nothing ever really goes away. Adopting the way archaeologists view the world - as a set of layers, some closer to the surface than others - is the only healthy solution to our society's neurotic swings between obsession and amnesia.
All of this is a way of saying that the plans to drive a big motorway through this sacred landscape are the epitome of the crass, vulgar values that now holds sway here. The M3 will not go through the Boyne Valley, but it will bisect the spiritual centre of the world of those who built and used the Boyne Valley monuments. It will include a huge 34-acre floodlit intersection a kilometre from the Hill of Tara which has been, as Dáithí Ó hÓgáin puts it, "a sacred centre from time immemorial".
As a stellar array of national and international scholars wrote in a recent letter to The Irish Times, the Tara/Skryne valley which will be cut in two by the toll road, is "one of the most culturally and archaeologically significant places in the world ... it holds a special key to understanding the continuous progression of European civilisation".
The motorway will be of dubious value, and a number of perfectly sensible alternatives has been put forward. But it will be a nice little earner for private investors. The taxpayer will put up at least half of the €680 million cost, but whoever puts up the other half will get a 30-year licence to charge two separate tolls along its 47-kilometre length. The profits will be vast - probably double the size of the investment.
The decision to press ahead with this monstrosity is in itself an eloquent statement of contemporary Irish values. A few decades ago, there was a living memory in Co Meath of things that stretched all the way to prehistoric times.
Now, memory itself - the sense that there are layers of meaning both literally and metaphorically beneath our feet - is a bloody nuisance. There is money to be made and the prospect of cutting a few minutes off a journey. Anything else is an irrelevance. People, history, cultures, landscapes, the delicate web of connections that binds us to one another and to the earth, are so much debris to be bulldozed aside.
When the Taoiseach loftily dismisses all infidels to the great god of motorways as "swans, snails, and people hanging out of trees" he gives voice to a deep contempt for anything that can't be measured in tonnes of concrete and loads of money.