Not far from this magnificent cathedral, across the Potomac River, lies sacred ground - Arlington National Cemetery.
As the Americans here will know, it's one of two great national cemeteries administered by the U.S. Army - the other being at Gettysburg.
Many other American military cemeteries - some large, others small - are of course dotted across the globe. You'll find them at places like Pointe du Hoq in Normandy and Cambridge in England.
When democracies like ours go to war overseas, this is the enduring physical presence we leave behind: the graves of our young men and women.
Those graves are more than headstones, crosses, stars or crescents.
They're a profound statement of a nation's ideals.
Because when we see the names of the fallen on those graves we are forced to ask: why do they lie here under the cold earth? What brought them here to this battlefield to give their lives for others?
The answer to those questions will tell you much of what you need to know about the country they came from.
In Gettysburg the answer was provided by America's greatest President: to ensure that government of the people, by the people, for the people, shall not perish from the earth.
The men who fought and now lie at Gettysburg did so to deliver freedom. To abolish slavery. To make it absolutely clear that the principle upon which the nation was founded - that all men are created equal - would be more than just words. They wanted that idea to guide the nation's behaviour towards its own citizens and towards all the peoples of the world.
My country - Australia - has a similar place where our founding ideals were tested and triumphed. And where our young men's bodies still lie in obedience to those ideals.
It's a peninsula well known to the Australian, New Zealand, British and French citizens here today as Gallipoli - and to the Turks as Canakkale.
And it's a peninsula that plays a central role in one of the most important days on Australia and New Zealand's national calendars.
ANZAC Day,marked onthe 25th of April each year, commemorates Australian and New Zealand service men and women whose lives have been lost on active duty, and those who have served our two nations in war.
Between 25 April 1915 and 9 January 1916 men from Australia, New Zealand, the United Kingdom, France and other countries fought a torrid and ultimately unsuccessful campaign to capture this strategically important peninsula, force the Dardanelles, capture Constantinople and knock Turkey out of the war.
The losses were horrific. 2,700 New Zealanders. 8,700 Australians. 10,000 Frenchmen. 21,200 British. And more than 86,000 Turks.
And if you go to Gallipoli today - as many thousands of young Australians and New Zealanders do - you will see the memorials to them, erected on the very battlefields where they died: The Nek, Baby 700, Chunuk Bair, Lone Pine and Morto Bay. And you will inevitably ask 'why?' And 'what brought them here?'
I won't attempt to answer those questions for the other nationalities represented here today, except to say that for New Zealand and Turkey, the Gallipoli campaign played an important role in their evolution as modern nations.
But let me try to make sense of it for Australia.
When the Australian states formed into one nation in 1901 we adapted to our conditions many democratic institutions and rights drawn from like nations. For instance, our federal system and our Senate were partly modeled after America's example. We were young, modern and progressive.
And like America we also had a central animating idea - for us it was the egalitarian notion that any person was as good as another.
In 1915 Australia was far from classless, but we were less constrained by class than most.
Our ideal was no master, no servant, just individuals bound together as equals.
In fact Australia's first two prime ministers during the First World War began their working lives as nine-year-old pit boys. The third as a labourer.
Australia discovered the truth 'that all men were created equal' through our own hard experience.
The story of Gallipoli and the even more bloody campaigns that followed in France, Belgium and Holland illustrated this rough and ready equality.
Like any founding story, that time is shrouded in myths and legends, but some facts are irrefutable. Officers and soldiers - who were both volunteers - were not treated as separate castes. A private considered himself as good as a lieutenant and a sergeant as good as a general. And our commanders valued the lives of their soldiers and spent those lives with the utmost reluctance.
These egalitarian ideals were not born at Gallipoli, just as America's ideals were not born at Gettysburg.
Australia was egalitarian from birth.
But at Gallipoli those ideals were tested - and proved their worth.
What emerged was a moral value that rapidly established itself as our supreme national virtue - a combination of bravery,resilience, the ability to improvise, and the duty to stick together in hard times and protect your friends.
We summon these values again today, as we confront together the human cost of aglobal recession that has reached our own shores - theworst since the Great Depression.
I'm of course talking about'mateship'.
Since our earliest days as a nation, this ethos has had a powerful hold on the Australian psyche ever since.
Like most national ideals it's often honoured in the breech. But whenever we fall short of it, self-censure is never far away. Our consciences drag us back to where we know we should be. Every generation re-interprets 'mateship' it in its own light. From an exclusively male and Anglo-Saxon ideal, it's now been transformed into something inclusive of everyone.
It's a culture that was implanted directly into my own family.
In America, the proudest boast is that an ancestor fought with Washington, or with Lee or - as with President Obama's grandfather - with General Patton. For an Australian the proudest boast is that your ancestors fought with General Sir John Monash.
Monash was the military genius who emerged from Gallipoli to become commander-in-chief of the Australian Corps in France, and who in July 1918 commanded ANZAC, British and American troops at the decisive battle of Hamel. It was the first time Australian and Americans fought side by side and, in honour of US troops, Monash launched that battle on July 4.
My own grandfather was such a man. Stirred by the story of Gallipoli he enlisted straight away, and was accepted one week after the peninsula's evacuation, to help make up the crippling losses the AIF had suffered.
He eventually became part of Monash's 3rd Division, serving in the trenches on the Somme and in Flanders - where he fought at Ypresand Broodeseindeand received serious shrapnel wounds during the taking and holding of Messines Ridge.
In 1918 he helped stop the great German Spring Offensive on the Somme Valley at Morlancourt - where he was likely gassed for the second time and wounded by shellfire once again.
His son, my father, served in the Second World War - also proudly alongside Americans, in the RAAF, where he too was shelled, bombed and attacked by enemy infantry, constructing airfields on Tarakan and Balikpapan in 1945.
Like his father, he saw mates killed. This is something he never forgot. He too was infused by the ANZAC spirit of looking after others, and although a working man who never owned much, he devoted his post-war years to helping his fellow veterans and their widows and dependents, eventually becoming secretary of his local Returned Services League.
What my grandfather, my father and those who lie in numerous graves across the world believed was this: that a nation founded on the idea of equality is a nation worth fighting for.
That's what ANZAC Day means to me.
And now a new generation continues the ANZAC spirit.
Today we honour all the men and women in harm's way in numerous conflicts and peacekeeping missions around the world.
Young Australians are currently fighting alongside Americans, Britons and numerous others in Afghanistan. They're there for many reasons - principally to fight terrorism.
But they're also there because a fundamental part of their make up says they must go.
Because when they see a family bullied by fundamentalist extremists, or a young girl denied the right to an education, or a young boy conscripted to fight for a cause in which he doesn't believe - in short, when they see the idea of equality trodden in the dirt - they know this is a cause worth fighting for.
That value of equality was proclaimed at Australia's birth. It was proven at Gallipoli. And it continues to guide us today.
Thank you.