"Anything further, father?"

Groucho, gazing at his offspring with affectionate contempt, repeats the question. "Anything further, father? That can't be right. Isn't it anything father further?"

I reserve the right to make jokes; a family habit in difficult times. The exchange is from an antique Marx Brothers movie, and through endless repetition, it became a kind of code between father and son, imbued with entirely personal meaning. Groucho - and Dad - would continue: "I married your mother because I wanted children. Imagine my disappointment when you arrived."

I write this with Echo, the family dog, sitting at my feet. As regular readers will know, my father, when trying to find sense in a world that contained infuriatingly little, sometimes imagined conversations between himself and the canine, who looks upon humanity with justifiable bafflement. Today, Echo's confusion is of a different sort: he doesn't know where his favourite human has gone. I know the feeling.

The loss of a loved one is an injustice we shall all suffer. It cannot be undone or defeated. Dad battled against all those that could. What's more, he showed the rest of us how to do so. So who was the man who taught us - who taught me - so much?

He was a communist. When many who have no apparent problem with monarchy, privatisation and legislated injustice call themselves 'socialists', he preferred - as he always did - a word more honest in its precision. It frightened the right people.

He was a nationalist, because he believed self-determination was a prerequisite to liberation in any form that matters. Yet he knew that nations do not have destinies; they have people, a resource infinitely greater in value.

He was a writer. He shared with Gore Vidal the belief that one is born a writer, and that there is little the victim can do about it. Which is, of course, no excuse for not putting in the work.

Others have spoken of him as a journalist, a friend, an inspiration. Only I can speak of him as a father, a privilege I share with no one. Parts of that experience, and the knowledge that comes with it, shall remain private.

Even he didn't fully understand it. Once, during my adolescence, I tried to express how proud I was of him. "Why?" he answered immediately. I had innumerable reasons, but I knew that none would ever satisfy the standards which made him his own most unforgiving critic. While I struggled for words before a man who had mastered them all, he said, almost apologetically: "You will never get a break with me, Sean." That was the burden and the gift he left me.

Let it be stated plainly: he was an extraordinary father. Many of his qualities were unique to him alone. Others would be recognisable in any loving parent. Throughout his entire career, he only once had an secretary. Her first, most significant task? Track down a Ghostbusters Fire House before Christmas Eve.

He cared deeply about both the Scotland that is, and the Scotland that could be. He fought, with all the weapons in his considerable arsenal, in the hope that they might some day be one and the same. My hope is that the country which gave him comfort, even when it failed him, understands what it has lost.

In our admiration, we should not forget those who made him humble: first, the honest, impossibly kind working-class parents who, to his eternal astonishment, never made a single enemy, and taught him to appreciate the democratic intellect.

Then, a wife whose lineage existed in defiance of the Armenian genocide, whose life existed in defiance of cancer, and who, by mysterious magic, made their love into a song that lasted a generation.

And finally, an ancestor who left him with a cause to defend and work to be completed. James Connolly, tied to a chair before a British firing squad, showed us exactly how to deal with grief. We mourn, and then we go back to work.

The work remains incomplete, and perhaps it always will. The undeclared worker's republic was always, in part, a republic of the mind. It exists there still. One and all can be citizens, if they're prepared to try.

As a student, he wrote his dissertation on The Tempest. The affinity he felt for Prospero was understandable - all-powerful to his adversaries, powerless before those he loved. "Now my charms are all o'erthrown, and what strength I have's my own..."

It was a strength built from words, integrity and ideas. In the wake of tragedy, it nourishes me still. Let it nourish all who would recognise it. Let that be his legacy.

I will spend the rest of my life in my father's shadow. There is nowhere more illuminating, and nowhere I would rather be.

Goodbye, Dad.