“You can fall into the trap of thinking that consumption is all that matters for people’s lives,” he tells Eternity. As one of Australia’s best-known economists, a board member of the Reserve Bank of Australia and the dean of the Melbourne Business School, Harper is more often than not thinking about wealth. After all, he tells me, that is what economics is all about.

“What would you know about being on the minimum wage?”

“Economics is the science of material prosperity,” Harper explains. “Economics can help us understand what it is that can make us richer materially, rather than poorer.”

Harper has spent a lifetime studying the things that make us richer: “how to help people have more ‘stuff,’” as he describes it. In this moment of Marie Kondo de-cluttering fanaticism, that might seem like a strange, unhelpful occupation. But Harper says he’s not embarrassed by his profession or its emphasis.

“Stuff is important to people. But ‘stuff’ is broad: it includes health, education, parks as well as fancy cars, nice dresses and shoes.”

And, says Harper, as a Christian he knows that’s not all that people need. “I think people know deep down that material possessions can do an awful lot, and that’s good. But there’s more to life than that.”

In his updated book, Confessions of a Meddlesome Economist, published late last year, Harper writes about his lifetime of economic prowess and his striving to keep one eye on the people that his work affects. He says his Christian faith has helped him promote the individual worth of human beings, which can sometimes get lost in an economic world that emphasises the production of goods and services.

As the inaugural chairman of the Australian Fair Pay Commission from 2006 to 2009, Harper and four commissioners were charged with setting the minimum wage. He said he was often criticised by people who asked: “What would you know about being on the minimum wage?”

“It was a perfectly legitimate question. I was a well-paid academic. But, as was required by legislation quite rightly, we were talking to these people. So I could answer, ‘Well, I spent the morning interviewing eight people on the minimum wage about exactly what it’s like. When was the last time you spoke to someone on the minimum wage?’”

Harper recalls one man in an interview session who was asked to write down what his life was like on the minimum wage. “This one chap was just playing with the pen, just doodling. It dawned on me after a while that perhaps he couldn’t write. I don’t know for sure. But it was this same chap who gave the most insightful answer when I asked him what the minimum age should be.

“He said, ‘Oh well, part of me thinks I should be paid $1000 an hour. After all, I can’t live on what I’m being paid now.’ But then he stopped and said, ‘But I suppose if it was $1000 an hour, no one would give me a job.’”

The man’s answer, says Harper, summed up the challenge of his role on the AFPC. “Balancing the justice, if you like, or the capacity of the wage to afford you a decent living and the affordability of that wage to an employer to pay you that.”

“[When I told him that] the man looked at me and said, ‘Right, mate. If that’s the case, I wouldn’t want your f***ing job for quids!’”

As it turns out, there were plenty of people who didn’t want Harper in the role of chairman of the AFPC. Harper pinpoints that part of his life as “the greatest personal challenge” he has faced.

The AFPC was created under the Howard government’s controversial WorkChoices industrial relations laws. Harper says he had to deal with trying to “retain the confidence of people as they struggled with the decision to create a new institution to set the minimum wage,” while also being publicly identified as a committed Christian, triggering media headlines such as, “God to guide deal on fair pay”.

“I’m not alone in occupying public office and being a confessing Christian, but … it was the closest I’ve come to being mocked for my belief. I think it’s a deeply un-Australian thing. It’s pretty unattractive. I’m not conducting some secret rite or sacrificing animals. What goes on in a Christian church is a matter of public record. What we believe is written in a book … none of it is concealed by anybody. I’ve made no secret of the fact of what I believe.”

“In my profession there is a temptation to measure people’s worth according to their material wealth.”

Harper says his faith and church community at St Jude’s in Carlton, in Melbourne’s inner city, has kept him grounded in a way he might not otherwise have been in the positions he has occupied.

“St Jude’s in Melbourne is right next door to the University of Melbourne, in one of the most rapidly gentrifying parts of Melbourne. Inner Melbourne has become very wealthy, with these islands of exception – the public housing estates – where there are refugees, people suffering from various levels of incapacity through mental illness and addiction.

“It is a great reminder of the breadth of God’s church but also of the people whom God loves. In my own congregation, there are surgeons, scientists, architects, lawyers, and there are people who haven’t got a job. There are young people, old people, people who haven’t worked in years, who can’t speak English, who’ve just arrived by boat. It’s the whole panoply. Yet they all recognise the Lord Jesus, praise God! And for all their differences, they’re brought together in communion.

“It gives me an entree into aspects of life that as a professional economist, at my end of the profession, given my age and where I happen to be and the boards I sit on, I would likely have nothing to do with some of these folk. But the church reminds me that that’s not how God sees it.

“In my profession there is a temptation to measure people’s worth according to their material wealth. And yet the gospel says exactly the opposite. In church each week, more or less, I’m reminded that that’s not how God sees us. That’s not how he assesses our work. It’s a beautiful thing. And it’s part of the reason that I’m a follower of the Lord Jesus.”