The journey of his struggle and that of his tireless, devoted parents Leona and Stephen, with the scourge of neuroblastoma, was impossibly painful, nasty, heart-breaking and was such a marathon of suffering and incredible hope that it was quite stunning to realise on the morning after his death that Oscar was only five years old.
It's human nature to try and find meaning, solace and understanding when faced with unutterable tragedy. We need to fight chaos with order.
But sometimes there are events so desperately sad they seem to rob our very existence of any comfort. The death of a child is one such time, and the universe, the natural order, call it what you will, seems to cry out in agony. Today, in some ways, there seems only pain and the echo of that pain. But there is something else. There is how Oscar left us; changed, bigger than ourselves, better people.
There are many stories visible now, especially with social media and the several routes there are to raise awareness and foster campaigns, of breathtaking endurance and inspirational effort. One thinks immediately of Una Crudden's fight to the death to save other women from the ovarian cancer that is killing her.
But what distinguished Oscar's life was how much of it he managed to cram in to so few years, how many hearts he won, how high were the barriers he crossed, how seemingly unbridgeable the divides he bridged – how deeply he planted his small footprints into the very fabric of our daily lives in this blighted, self-obsessed, persistently-bickering, rash and often dangerous place we live in.
It used to be routine – maybe it still is – for the media to describe people with terminal illness as "brave" or "courageous" or "plucky", by virtue simply of the fact fate has dealt them a formidable hand.
And there is something about how one – anyone – might respond with vigour to such a diagnosis rather than, quite understandably, lying down under it with honest despair which can appropriately be characterised by the word "courageous" without detracting from the bravery of emergency services or spontaneous life-savers or those imprisoned or murdered for their beliefs.
But with wee Oscar, there isn't and wasn't even a moment's hesitation for us as a society to recognise the profound depth of his courage and the incredible scale of his spirit.
It was instantaneously obvious from his diagnosis in 2011, continued through his seemingly miraculous recovery early last year, and returned with only a renewed clarity, a more obvious force and deeper conviction even as the neuroblastoma came back last autumn finally to claim its tiny victim on Thursday afternoon.
None of this was about the disease. It was all about this small person and how he became, because of it, a national sensation thanks to his desire for life in the face of it.
In a way, neuroblastoma was only the platform, the occasion, for Oscar Knox to live a life to the full in such a dramatic fashion that it, quite frankly, shames the rest of us – not that shame or regret were experiences any of us learned from Oscar Knox's life, which was one of fierce attachment to family, joy, friends, fun, exuberance and absolute openness to the kindness of strangers.
We are all strangers to each other. Many of us are strangers to ourselves. But those many, many thousands of us who were bound by whatever strong, instinctive cords of compassion, identification, sympathy, to the narrative of this small boy's life were all, for more than a moment, friends and allies.
This isn't some sentimental wishful thinking. The bonds of affection weren't the easy option for otherwise disparate and often opposing forces to display a human face. They were real. They are real.
The First Ministers welcomed Oscar to Stormont. Hundreds gave blood at the City Hall in his name. Sports stars like Paddy Barnes, Michael Conlan and Carl Frampton came out fighting on his behalf. Football's Old Firm stood as one behind him.
Oscar's life – not his illness, his suffering or, now, his death – is and was what channelled such vast resources of goodwill, prayer, best wishes, and, when needed, assistance.
His life was a gift to all of us, not from his family to us, though the intensity of grief will be theirs most intimately and privately this weekend and for the rest of their lives.
The gift was from Oscar himself and was Oscar himself. The lovely smile.The determined thumbs-up from his hospital bed. The superhero outfits. Our braveheart.
In a society likes ours, past and present, which seems always to be about division and subtraction – of communities and lives – Oscar's life was all about giving, all about adding to, all about augmentation and amplification, all about plus and multiplication.
That's why, as a society, we owe people like Oscar Knox, big time. But, for this morning above all mornings and for many, many mornings to come through our own lives, we owe Oscar Knox himself big time.
The Belfast poet Louis MacNeice said on all our behalfs:
God or whatever means the Good
Be praised that time can stop like this,
That what the heart has understood
Can verify in the body's peace
God or whatever means the Good.
God or whatever means the Good rest you, Oscar Knox. Thank you for your wisdom.
Donations to raise money for the Northern Ireland Children's Hospice in memory of Oscar can be made via a dedicated JustGiving page at justgiving.com/oscarknox.
In 2011 Oscar Knox (5), from Mallusk, was diagnosed with high-risk neuroblastoma, which affects one in every 100,000 children. He also has the chromosome disorder Jacobsen syndrome, which is thought to affect only 250 children worldwide.
Oscar has received more than 30 blood transfusions and almost 140 platelet transfusions in the past 26 months. Oscar's parents Stephen and Leona run a blog and fundraising campaign, The Wee Oscar Knox Appeal. Around 140,000 people follow Oscar on Facebook and Twitter @Wee_Oscar