It's one of those perfect autumn Sundays, when the sun is warm without being fierce, when the water is still warm, and when the retreating tide reveals the sandbar of the river estuary.

It is here that we play, the three of us, creating sandcastles that collapse into the water almost as quick as we can build them.

The spirits of the smallest boy, a six-year-old dynamo, rise and fall with his sandcastle - tears when the walls disintegrate into the water, triumph when he creates an edifice that remains.

As the sun sinks to the horizon and we find ourselves now almost alone as all the others have headed home, we swim the river that divides us from the shore. As my son follows me, kicking behind his boogie-board, he flashes me one of his radiant smiles.

"Dad! That was the bestest beach day ever!"

It is a flash of happiness that makes everything else worthwhile, yet it is fleeting, unexpected and gone far too soon.

"Exactly," Hugh Mackay might say. "Exactly why it is foolishness to build your life - like a crumbling sandcastle - around the pursuit of happiness."

But more than that, Mackay would argue that true happiness can only be seen as a reflection, seen in other people.

"No one can promise you that a life lived for others will bring you a deep sense of satisfaction, but it's certain nothing else will."

Mackay retired from his career as a social researcher in 2008, after 50 years of listening to other people, and is writing about the conclusions he has drawn from a thoughtful life.

He's a difficult interview, nevertheless, because he can't help himself - drawing other people out and hearing their experience when the point is to discover what makes Mackay tick.

Now aged 75 and an honorary professor of social science at the University of Wollongong, he has followed up his previous book - What Makes Us Tick - with what can be seen as a companion and sequel - The Good Life.

"This is not a young man's book, though I hope it is a young man's or woman's read," Mackay says.

"I wouldn't have been game to write this book 10 years ago."

In What Makes Us Tick, Mackay draws up 10 social desires that drive us, the most important of which is that we all wish to be taken seriously.

In his latest book, Mackay takes this further, building his argument for a good life (as opposed to a happy life) around the Golden Rule - to treat other people in the way that we would like to be treated.

This puts us in fundamental conflict with the fashionable belief that we should pursue perfection.

That we are all owed a happy life, a kind of personal utopia where we strive for self-actualisation above all else - the perfect teeth, the perfect breasts, the perfect house, the perfect work, the perfect family.

We need to strive to know ourselves, to maximise every opportunity to be the best we possibly can be, to fulfil our potential and to have a good time. If - God forbid - we experience emotions that are difficult, challenging or dark, then we should deny them with distraction, therapy or drugs.

Mackay's gentle polemic against what he calls the happiness culture, is a call to return to those old-fashioned virtues of living a life for others, rather than for ourselves.

It's a radical shift in perspective. Instead of "Who am I?", we should be asking "Who needs me?"

Although not religious, Mackay describes himself as "a Christian agnostic", it is no accident that his ideas are shot through with ideas that are common to all the major world religions.

Born into a Baptist family, Mackay was born into a fundamentalist religion where the Bible was read daily and Sundays were devoted to God. In his late teens, Mackay even contemplated joining the clergy and his manner even today - thoughtful, compassionate and caring - makes it easy to imagine.

By his mid-20s, however, he had studied philosophy and psychology was experiencing a religious crisis of faith that led him out of the church, never to return.

"When I reflect on this, maybe even five years ago, I would have said it was a very bruising experience and I was damaged by all of that," he said.

"Now, I would say that was true but also that I benefited from it all enormously.

"I did know a lot of cultural stuff from Biblical stuff that's been very valuable and I also got a particular view which sparked my whole interest in morality. There are lots of things that I value about it retrospectively."

Not least, Mackay has never lost his interest in the ideas of God and good, even singing in the choir of the liberal-minded St James Anglican Church in Sydney, where he is still an occasional parishioner.

"I have tried, increasingly as I have got older, to put the needs and well-being of the people I encounter ahead of my own," he said.

"Over the last 20 years, I have understood that a good life is not about having a good time or feeling good. A good life is about goodness.

"There's a point in the book which I regard as the kernel, even the proof, when I ask, 'What is the most powerful force for good in the world?'." The answer is love.

"All the manifestations of love, such as compassion and kindness, only make sense if you think of them as in the context of a relationship or a functioning community.

"Therefore, goodness can only be about others and how I treat others."

Perhaps the most challenging part of the book - prefaced by an invitation to skip it for those of a squeamish disposition - relates to the fictional story of Harry and his chicken fetish.

Harry is a 64-year-old divorcee, living alone and single. He is a good man, a member of his local church, a part-time auditor and an enthusiastic volunteer at a nearby school.

Although he is appalled by the idea of pornography, Harry is lonely and frustrated so develops a fondness for fresh chickens, which he buys from the supermarket and then uses for his weekly sexual gratification.

"Disgusting?" writes Mackay. "Revolting? Yes, to some of us; perhaps to most of us. But has Harry done anything wrong?"

Mackay argues that, because goodness is about how we treat others and there are no others involved in this practice, then Harry is still leading the good life.

"I am not terribly interested in private virtue, that's people's private business, I don't care," he says.

"Morality is all about recognising the needs of other people and responding to them respectfully."

Research for the book included going back to the philosophers and religious traditions where he discovered - time after time - versions of the Golden Rule.

"They all say the way we thrive is to treat other people the way we would like to be treated," Mackay said.

"It seems to me that we have known this for thousands of years. When we blot it out because of a materialist ethic, which feeds into the rampant materialist ethic, we do this at our great peril.

"We diminish ourselves."