What do we remember when we say we remember?

In truth, precious little. The world of 1914 is no longer available to us. They're gone, all of them. Those who once marched away are far beyond praise, pity, questions or sorrow.

When we stand before cenotaphs we stand, say the Greek words, before empty tombs. When we commemorate we recognise suffering. It may be we glimpse honour. Sometimes we give notice that we sense the human capacity for folly. But in remembrance of 1914 we do not, cannot, remember. "Empty tombs" is apt.

Memory is fragile at the best of times. A century on, we have memories of memories, tales told to children's children. Even when these are intact, even when someone has not misremembered what granddad said in bitter, mourning honesty, we are misled.

Granddad spoke; in the aftermath, legions of his comrades would not or could not speak. One legacy of the war they used to call great was a vast reticence, an enveloping silence. For every anecdote or learned study there were mute passing regiments of men who found words impossible or indecent. A century on, predictably, this too is being forgotten.

So we grasp at statistics or poetry. We seize on snaps and letters home. We count the names on monuments, restore scraps of film, stage exhibitions or study battle plans. Objects once commonplace, raised from harrowed soil, are held to be eloquent. The archaeologists long ago went to work in fields where men died, row upon countless row, with their memories.

When did that become decent? Where is history's statute of limitations, and what does it contain? Battlefield archaeologists treat all remains with reverence: that's not in doubt. There is an unspoken agreement, nevertheless, that a moment arrives when the dead become artefacts, when memories have faded or disappeared, when the past no longer touches the present.

That's inevitable, if anything is, but after a century it renders remembrance and commemoration strange. Hence the statistics; hence the poetry. The first are meant to give us some sense of a war's inhuman scale; the second, we hope, will tell us how it felt to be human when all the world became hellish. At best, these truths are fragmentary.

Despite the poets, the old language grows stranger with the years, yet in speeches or sermons the Edwardian cadences persist. "The fallen", they say. Blown apart, cut to pieces, drowned, gassed, bayoneted, buried alive? Those men did not stumble into death. "Sacrifice", they add, never missing the chance to exonerate the present by means of the past. Sacrificed was always the better word.

Charles Hamilton Sorley was born in Aberdeen and killed at the Battle of Loos when he was barely 20. A sonnet, probably the last of his handful of poems, was found in his kit sent home from France after his death. It begins: "When you see millions of the mouthless dead/ Across your dreams in pale battalions go,/ Say not soft things as other men have said,/ That you'll remember. For you need not so."

Captain Sorley, a fond admirer of Germany and Germans, already understood what all the war poets in time understood. No matter how beautiful or moving their lines, no matter how truthful, war's reality was inexpressible. Words always failed. Poetry whispered into the abyss.

"It is easy to be dead," wrote Sorley, promoted to captain with his wisp of a boy's moustache barely six weeks before a sniper's bullet found him. His last poem refused praise, tears and honour. For the dead, these were meaningless, and he rebuked the living: "None wears the face you knew".

All war is like that, no doubt, but few wars have contained the stench of absolute eradication that swept across Europe in a great cloud in 1914-18. It touched everything, everyone, everywhere. The forests of monuments, across Scotland and beyond, show where it passed. The folk image is of men and boys clambering from trenches in their millions to walk into the consuming cloud. There's truth in that, but not the whole truth.

The generation of those maimed in body and mind, lingering for years and decades, outnumbered the dead many times over. The men who were ashamed of their medals, even of their survival, kept remembrances to themselves. For many, helpless anger and disgust swamped all the naive pride of August 1914.

Today, even statistics need to be handled with care. You can discover, for example, that of 8,689,467 men from Britain and its empire who were under arms during the war, 2,272,998 were wounded. You can learn that just 8 per cent of these were discharged as invalids, that 7 per cent died of "wounds received". But those who recite figures forget the idiotic bureaucracy of war: if a man was wounded more than once, he was counted more than once.

For Scotland, statistics have bred myths even when reality was terrible enough. It is a commonplace, for another example, that "150,000 Scots died" in 1914-18. After all, the rolls housed at the National War Memorial in Edinburgh contain almost that number of names. If 704,803 of the men who joined up in the British islands died - such is the official tally - Scotland's contribution was, astoundingly, in excess of 21 per cent.

The toll was indeed astounding, but the figure is deceptive. The national memorial's criteria specify that the dead had to be Scotsmen, born of a Scottish parent, or - crucially - those who "served in a Scottish regiment". Even before the war began, such regiments were never composed entirely of Scots. Once the carnage was inaugurated regiments were "diluted" repeatedly, in any case, with whatever reinforcements were at hand.

What of it? If just 70 per cent of the members of Scotland's regiments were natives, you realise with shock and wonder that around 15 per cent of Britain's war dead came from this small country at a time when Scots accounted (says the 1911 census) for 10.5 per cent of the population of Great Britain and Ireland. Ponder that fact and a couple of other truths come to mind.

First, Scottish regiments were in general infantry units, and therefore prime candidates for the charnel houses. Secondly, Scots joined up in numbers that almost defy modern comprehension. Total recruitment from Great Britain and Ireland over the course of the war saw a staggering 4,970,902 men put in uniform. Of these, to add to those already serving in August 1914, 557,618 were recruited from within Scotland. If statistics are your taste, that was 11.22 per cent of military manpower from these islands.

That still isn't quite the story. There remains something mysterious about Scotland and the war, something that is not captured by arguments over purblind generals or imperial shock troops. No-one forced the Scots to give more than their population share. Conscription doesn't explain it. "Martial traditions" might answer, but so might a loyalty to Britain and empire that has long gone. Do those convince?

In the welter of statistics, one retains the power to explain why grief ran so very deep. According to the census, the population of Scotland was 4,760,904 in 1911. Allow that perhaps the figure had edged up a bit by August 1914. Even so, with 557,618 recruited from the glens and fields, the suburbs and slums, at least 11.5 per cent of the entire population of the country went to war. Approaching one in five did not return.

For what reason? Modern historians of the conservative sort will tell you either that the war had to be fought to halt German aggression, or that there was no reason for Britain to become embroiled in 1914. Conservative politicians of Michael Gove's stripe meanwhile itch to celebrate loyalty, duty and past glories. Earlier this year, the former education secretary was insisting that the slaughter be called just. He spoke up for king, country, and something he called the western liberal order.

Mr Gove forgot to say that most of those he claimed in freedom's name were denied the right to vote in 1914, and that all the women they left behind were so denied. Overlooked was the fact that on the eve of war life expectancy in Britain was just 55, or that the Conservative Party had opposed tooth and nail even the modest social reforms introduced by the Liberals before the bugles sounded.

In this summer there will be regrets for the poetry that never was. What might young Sorley have achieved? What might they all have achieved? Should we contemplate the big numbers and the aching words a few regrets can be spared, perhaps, for an entire world that never was.

Philosophers, trade unionists, poets, engineers, doctors, farmers, painters, railwaymen, politicians, miners, seamen and soldiers too: you could as well list the varieties of human endeavour. You end up, always, with sons, brothers, fathers and all the fathers who never were. You end up realising that you cannot stand in remembrance for all the lives denied by war.