Everyone, it seems, has a take on the faith of Australia’s new prime minister.

Some are excited (others anxious) that we now have a Pentecostal in the Lodge. His pastor has appeared on national television reassuring us that the PM is an ordinary bloke. Even Graham Richardson has chimed in, suggesting, somewhat bizarrely, that Scott Morrison’s faith is off-limits. Then there are the longstanding debates about church and state that come to surface whenever a Christian assumes high office.

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But, as we’ll see, this commentary is missing an important element. Morrison is already familiar with his faith being scrutinised.

The authenticity of his Christian faith has often been called into question on account of his oversight of Australia’s treatment of asylum seekers.

Certainly, it is hard to reconcile the Christian faith to the sheer hard-heartedness with which the prime minister and other Christians from both the Coalition and the ALP have implemented and defended their immigration policies.

But scrutinising the moral consistency of Christian politicians is only half the story.

Beyond their morality and beyond the discussions about separating church and state, there’s another matter that largely goes by without comment. It’s this: what kind of theological ideas are Christian politicians injecting into public debate and using to buttress their politics?

This should rightly interest both Christian and non-Christian like. And Morrison provides an interesting case study.

In his maiden speech in 2007 Morrison put his Christian cards squarely on the table. He invoked Abraham Lincoln: “Sir, my concern is not whether God is on our side; my greatest concern is to be on God’s side.” It sounds benign, but it isn’t.

Deep in the logic of Christian faith is the idea that God is impartial

We need to dig deeper to see what’s going on here, and to set it against two trends emerging in the way Christian politicians talk about their faith.

One is the heavy-handed defence of the so-called Judeo-Christian tradition. This is the argument of such cultural warriors as Tony Abbott and Cory Bernardi. Their argument is that because western culture has been shaped by Christianity, somehow it is the responsibility of our political processes to advance Christianity and to protect the west from other religious influences – especially, it turns out, those of Islam.

This whole approach rests on a mythical idea of the “Judeo-Christian tradition” but that’s another story.

The other trend is more subtle and much closer to the prime minister’s style. It is the way politicians talk in highly personal terms about the ways “faith”, “my faith” or God “guides”, “helps” or “strengthens” them and/or gives them their “values”. A striking example of this occurred in the 2016 US presidential election.

On the Sunday before election day a campaign video of the Republican vice-presidential candidate Mike Pence was shown in many American churches. It was a blatant attempt to shore up the so-called “evangelical” vote. In genteel, reassuring tones, Pence told the story of his faith largely in terms of family, community and nation.

“Faith” was presented as a vocation to, quite literally, “make America great again”. It was politically astute, far from benign – and utter theological nonsense.

Strikingly, he too quoted the same words of Lincoln that our new prime minister cited when he entered parliament. While Morrison doesn’t invite the description of genteel, there is a common thread of the Christian politician as a family man reassuring the Christian constituency.

In that maiden speech, at least Morrison was more theologically aware than Pence. After quoting Lincoln, he invoked the South African archbishop Desmond Tutu to sketch his vision of what it means to be on God’s side. Tutu’s words were presented as his benchmark: “We expect Christians ... to be those who stand up for the truth, to stand up for justice, to stand on the side of the poor and the hungry, the homeless and the naked.” Of course, it is exactly these words that have been thrown back at Morrison.

It is just as important that Morrison stay alert to the way his chosen language of being “on God’s side”, benign though it seems, is fraught with danger, not least when employed in the partisan, adversarial world of Australian politics.

For instance, if I convince myself that I’m on God’s side, then what of those who oppose me? If I believe that I’m on God’s side, I can easily relieve myself of self-criticism and ignore the criticism of others.

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The notion of taking God’s side also invites a certain kind of false heroism that easily slides into triumphalism. In the end, convincing yourself that you’re on God’s side is actually just a bit too close to thinking that God is on your side after all.

Deep in the logic of Christian faith is the idea that God is impartial. The only “side” that God’s takes (if that language must be used) is the side of all humanity. This, moreover, is why those Christians welcoming Morrison’s elevation to the prime ministership as indicating some sort of benefit to Christians are so wrong in their understanding of Christianity.

When the prime minister handed out badges of the Australian flag to his cabinet, he did so to remind his ministers that they were “on the side of the Australian people”. Let’s hope he remembers that the God he believes in sees right through the jingoistic badges worn by politicians and has concerns much deeper than those of Australian patriots or family man style-Christianity. Those deeper concerns, acknowledged in Morrison’s maiden speech, should be shared, lived and politically enacted by all of Australia’s Christian politicians.

• Geoff Thompson lectures in Christian theology at Pilgrim Theological College within the University of Divinity