Earlier this year, Edward Hirsch, who has dedicated his life to the writing, reading and teaching of poetry, published what critics widely acknowledged as the definitive handbook of his vocation. Hirsch is 64. A Poet’s Glossary was 10 years in the making and a natural sequel to his bestselling and passionately informed work How to Read a Poem. With entries ranging from “abecedarian” (“An alphabetical acrostic in which each line or stanza begins with a successive letter of the alphabet”) to “Zen poetry”, it runs to 700 pages.

The glossary was organised alphabetically, and among the terms Hirsch defined, naturally, was the poetic notion of the “elegy”: “A poem of mortal loss and consolation,” Hirsch wrote, crisply, citing examples from ancient Greece to Thomas Hardy, before going on to elaborate on such a poem’s function: “The elegy does the work of mourning,” Hirsch argued, “it allows us to experience mortality. It turns loss into remembrance and it delivers an inheritance. It opens a space for retrospection and drives wordless anguish, wordless torment toward the consolations of verbal articulation and verbal ceremony.”

What that carefully crafted description stopped short of saying was that Hirsch himself, while researching his book, experienced just such a mortal loss, and just such wordless anguish and wordless torment. On 26 August 2011, on the night that Hurricane Irene screamed into New York, Hirsch’s only son, Gabriel, aged 22, went out to meet a friend for a drink. He ended up at a party in New Jersey, following a lead on the website Craigslist. At the party it seems he was given a club drug, GHB, probably in a drink. Gabriel, who had been diagnosed with Tourette’s syndrome as a child, and who was at the independent end of the autistic spectrum, became violently sick and had a seizure. An ambulance took him to a hospital, where he died, shortly after six in the morning, from cardiac arrest. Hirsch and his ex-wife, Janet Landay, did not know these facts for three days. Hurricane Irene and its fallout was occupying the city police who had no time to search for missing 22-year-olds with known nocturnal tendencies. The poet himself wandered the storm-battered city in search of his lost son before eventually finding him at the hospital morgue.

For a year after that Hirsch was unable to do much of anything at all. He had read a poem, or a book of poems, every day of his adult life, he says, but now he could not read. He moved to Atlanta for while, where his partner, Lauren Watel, a writer, lived, and then spent some hours of each day obsessively making what he calls a “dossier” of Gabriel’s life, talking to friends and relatives about their memories of his son, compulsively collecting fragments of anecdote and biography, collaging his life together. After about a year of this, after he had spoken to everyone he knew with anything to tell, Hirsch found, inevitably perhaps – old habit dying hard – that some of those collective memories started to shape themselves into poems. Eventually, he came to a form in which he felt he could begin to accommodate something like his loss, and something of the texture of his son’s vibrant, chaotic life, and earlier this year he completed a 70-page book-length poem called Gabriel.

The poem has just been published in America; the New Yorker called it a “masterpiece of sorrow”, and you wouldn’t argue with that description. Reading Gabriel is both a shattering and profoundly human experience; Hirsch’s unfathomed loss is measured against his son’s brim-full existence. The poem tries – and gives up trying by turns – to capture a son’s spirit that refuses constantly, properly, to be quite contained in his father’s words. From a man who you could think of as a professor of the elegiac form and its possibilities, it is an uncompromising and tender elegy like no other.

Hirsch’s office is on the 33rd floor of a building in Manhattan adjacent to Grand Central station. For the past 11 years he has been president of the John Simon Guggenheim foundation, responsible for the supervision of the $240m endowment fund and the allocation of 200 grants per year to support significant work in scientific research and the arts. His corner office affords a view of both the Hudson and East rivers; the Empire State Building dominates the foreground. The two walls that aren’t glass are lined with his personal collection of thousands of books of poetry, and he seems at home among them. He has a somewhat wary presence – the more so no doubt because of the subject of our interview – and a poet’s unstinting alertness to saying what he means, but he is quick to smile, too, and warm in his welcome.

In the days before meeting him I have been reading Gabriel, and wondering exactly how I might begin a conversation with him about it, so raw does it seem. The poem is written in quite loose and conversational three-line stanzas, a quiet echo of the terza rima, the chosen form of Dante’s descent into hell in the Divine Comedy; it asks the reader to take something like the same journey with the grief-wrecked poet. Gabriel resists sentimentality at every line break, though it is the most heartfelt poem I have read. Along the way it digresses and finds an element of kindred feeling with elegies that have gone before – Tennyson’s In Memoriam and Mallarmé’s For Anatole’s Tomb – gestures to Hirsch’s lifelong reading, and in particular to elegies for the loss of a child, like Kochanowski’s Laments. It begins, though, looking its subject squarely in the eye:

The funeral director opened the coffin
And there he was alone
From the waist up

I peered down into his face
And for a moment I was taken aback
Because it was not Gabriel

It was just some poor kid
Whose face looked like a room
That had been vacated

One of the things the poem makes you do is face up to taboos surrounding our cultural fear or embarrassment of grief and the grieving. I say to Hirsch that one word kept cropping up in my head while I was reading, that ancient word “trespass”, as in the phrase “trespassing on private grief”, so we start off talking about that, about notions of public and private mourning, and the process of writing about death.

“The document, the dossier, I wrote after Gabriel died was really just for myself,” Hirsch says. “But as soon as you are shaping it into a poem you are not necessarily thinking of publishing it, but you are making it into something else – and that does imply a reader.”

Did he have a particular reader in mind when he was writing?

“I guess if I did it is some future reader who doesn’t know us, doesn’t know me and doesn’t know my son Gabriel,” he says, “and the only way that reader is going to know my son is through the burden of my poem.”

The great triumph of the book lies in that sense of getting to know Gabriel. Hirsch and Landay adopted their son, having spent many years in failed fertility treatment, when he was six days old. He was from the beginning “restive” and then quickly “reckless”. As a child he never, it seems, stopped moving or asking, and his life was as breathless and unpunctuated as Hirsch’s poem:

He wanted he needed to buy something
Every day a new video system an iguana
A baseball bat a football helmet

He wanted he needed to go right away
To the arcade in the Galleria
Where you won tokens that brought rewards

Someone told us he had King’s Syndrome
He thought he was royalty
And everyone should treat him like a king

We understood the desperation of the therapist
Who locked the door and sat on him
When he tried to leave the room

Out of the cumulative details the contours of a life emerge. What does Hirsch think his son would have made of his poem, I wonder?

“You can’t answer what your son would make of a poem about him because your son is not there,” Hirsch says. “A lot of my friends have been reassuring about this in that they say Gabriel’s personality comes through. Gabriel was not a shrinking violet, he imposed himself on a room. He wanted people to know him.

“I am also aware that there are things he didn’t like to talk about and wouldn’t have wanted known, but which are also part of his story. If you tell his story without talking about his disabilities, which he was embarrassed about, you wouldn’t be telling his story. He had all these tics, for example, which he didn’t like to acknowledge; but he had turned all those things quite triumphantly into a working person. It is me telling the story of Gabriel as a father. You go ahead because it is what you think is accurate.”

At one point in the poem Hirsch riffs on all the schools his son went to and was removed from for one reason or another:

He’s singing the Poe Elementary School blues
He’s singing the Shlenker School blues a day school
For the offspring of upper-middle-class strivers

He’s singing the Montessori School blues
He’s singing the Monarch School blues
For kids with executive function disorders

A page-long litany which finally comes to this dead end:

There are no more academies to attend
He was not befriended by study
A therapist called him one of the lost boys

He was a lost boy in the Peter Pan sense too, though, always adventuring. He once took a trip through the city lying flat on the top of a bus. His brief adulthood, with his friends, was a life of “try anything once”. He was “King of the Sudden Impulse/ Lord of the Torrent/ Emperor of the Impetuous”. He lived for storms.

I wonder what Gabriel thought of his father’s vocation as a poet? “He wasn’t a reader of poetry. He seemed to be pleased that I was a poet but that was it. Once I was at the Aspen poetry festival and Gabriel, not that old, was there with his mom, and we were just introducing ourselves, and Gabriel raised his hand and said, ‘We’re poets aren’t we, Dad?’ and ‘I said, yes Gabriel, we are poets’. He came to a few readings, he knew a lot of poets. But I wouldn’t say he was a lover of poetry. He used to like to say after I died he would burn all my books or give them away – he rather enjoyed tormenting me that way, as all sons maybe do…”

One of the things that Gabriel makes clear is that grief is not a selective process. Hirsch mourns all aspects of his son equally, and shifts quickly between moods and registers, reflecting Gabriel’s temperament – sometimes quickened or slowed by medication – and his own reaction to it. Nothing that is gone of Gabriel is left out. Hirsch mourns the sleepless nights of worry that he and his wife endured almost constantly.

Nights without seeing
Mornings of the long view
It’s not a sprint but a marathon

Whatever we can do
We must do
Every morning’s resolve

But sometimes we suspected
He was being punished
For something obscure we had done

I would never abandon the puzzle
Sleeping in the next room
But I could not solve it

Hirsch has clearly approached the publication of the book with trepidation. For one thing it does not appear to come with the full endorsement of his ex-wife, or at least she has no comment to make about it. Hirsch acknowledges in its endnotes how Landay “lived with me through much of what is recounted here, and has her own story to tell as Gabriel’s mother. We have different perspectives, as all parents do, but also a shared history, a united grief.”

Hirsch’s eight volumes of poetry – which have been garlanded with prizes, including a MacArthur award or “genius grant” – have always had a personal, confessional element, and he has written elegies before, to friends, but he sees the difference between that work and Gabriel as “like being in a wading pool and then stepping into the ocean”. In the end though, despite his wariness of the private and shared nature of much of this, he felt he had no choice but to publish the book. He wanted to give it a life of its own.

You also suspect that somewhere, deep down, he wanted to test his former faith. How to Read Poetry was in part an act of evangelism; great literature is offered as a solace, a replacement religion, a statement of shared humanity and an antidote to despair. There is a horrible irony in the fact that he has been called to test that faith in his own life. Did a part of him still trust that it would save him?

“I was a believer, and I am not any more,” he says. “When I wrote How to Read a Poem, I think I had a pretty good idea of what poetry could do for writers and readers, but this experience has brought home to me what poetry cannot do. I tried to put everything I could into my poem, I tried to do my absolute best, anything else would have been unworthy of Gabriel. But I am also aware that poetry has its limits. One of those limits is that poetry cannot ever give us back the people we have lost.”

Writing the poem was also an argument with a different kind of faith, Hirsch suggests. He was raised in a Jewish household but he was never a believer. In grief, though, he railed at a maker that he knew was a fiction. “One of the things that comes through in my poem, I think, is that I can’t believe in God but I can’t quite give him up either. I shake my fist at him, even though I know he isn’t there.”

He was unable to say the Kaddish, the prayer Jews have always recited daily in the first year of mourning, though he believes that 12-month period is a natural term for retreat into grief. He found people wanted to heal him in the extremes of his sorrow, or suggested medication, and sees the imperative to “move on” as a great misunderstanding in western society.

“I think ancient cultures incorporated death into the experience of life in a more natural way than we have done. In our obsessive focus on youth, on celebrity, our denial of death makes it harder for people who are grieving to fi nd a place for that grief. There is a big difference between depression and mourning. Depression is a feeling without a cause. Mourning has a cause. Many of us are carrying the dead around with us. We should not feel ashamed of that.”

He has, since his son’s death, felt that weight of grief as a physical burden, one he describes in a section of the poem:

I did not know the work of mourning
Is like carrying a bag of cement
Up a mountain at night

The mountaintop is not in sight
Because there is no mountaintop
Poor Sisyphus grief

Since he has carried that weight himself, he sees it in the bearing of others, initiates in what he calls the “saddest club on Earth”. “You are in that company,” he says. “Anyone who has lost a child will tell you that they don’t recover their sense of endless possibility. Some people hide that well. But after a certain age almost everyone is carrying something like that around, I suppose.”

On the opening page of Hirsch’s website he quotes from a poem that he was writing on the night that Gabriel went out into the storm. It is a poem for the troubadours of medieval France, and the verse runs like this:

I woke this winter morning
To the smell of the sea
And hummed a song for nothing
How nothing came to me

I wonder before I go if he reads into that verse now a sense of foreboding or premonition, of the nothingness he was about to experience. He says not, though of course he dwells all the time on the days when his son was missing in the hurricane, before he was lost.

“It is ironic that it is a poem about nothing,” he says, “but I love the troubadours, and it just happened to be what I was working on when Gabriel went missing. Its significance for me is that it is the end of my old life and my entry into a new one. I didn’t know at the time. But it’s a marker.”

One of the befores and afters includes some new thinking about that old disjunction between the importance of life and the importance of art. “I was always a little sceptical of poets as parents,” Hirsch says. “I used to play those games – you know: who were the best poet golfers, who were the best poet tennis players – and one of those games was who were the worst poet parents. There are plenty of candidates. I used, though, to be completely in the camp of everything for art. I remember, in my 20s, making the case for [Rainer Maria] Rilke’s total commitment to his work at the expense of everything else, including the daughter he fathered.” Hirsch smiles. “As you get older you begin to understand the claims of ordinary life and the claims of families.”

Before I left Hirsch to his evening, with the sun beginning to go down over that spectacular skyline, I asked him something that has been nagging at me throughout our conversation. I wondered if he wrote that careful entry on “elegy” in his A Poet’s Glossary before or after Gabriel died. “I wrote it before my son died,” he says. “And I didn’t rewrite it afterwards because I wasn’t sure I was in the best position to judge those questions in any way objectively.”

He paused. “If I wrote that entry again there would be far less emphasis on consolation.”

Gabriel: A Poem is published by Knopf Publishing