Pressed further, Turnbull obliged: "Our policies will change, all policies change. But when we do make changes we will do so in a considered way and they will be made by the ministers, the minister, myself, the cabinet."

In the combustible public space of asylum-seeker policy, "our policies will change" had dramatic consequences. For several hours news services led with this message, before the Prime Minister, having no doubt benefited from stern advice, forcefully retracted.

"There will be no resettlement of people on Manus Island and Nauru in Australia," he now insisted on ABC radio. "They will never come to Australia. I know that's tough. You could say we have a harsh border protection policy, but it has worked."

And all prime ministerial comments on the issue have been like that since then, lauding "hard heads" and deriding "misty eyes".

For the past decade and a half it has been routinely assumed that any tough talk on asylum seekers is primarily aimed at the electorate, but in this case the intended audience was further afield: the people smugglers and potential clients, mainly in Indonesia, where any perception of a "softening" of policy could see the boats start up again.

Similarly, in July 2013 the re-installed Kevin Rudd's new hard-line declaration, that no one who arrives by boat would ever settle here, was largely interpreted through an immediate political lens – Rudd was appealing to voters – but his motivations were somewhat longer-term: to slow the traffic before polling day.

And slow they did, dramatically – by more than a third in August, and then another half again in September. After that the new Coalition government's resolutely implemented turn-back policy all but terminated the traffic.

In this arena, such utterances matter, and there's little room for nuance. But inevitably the public language also conflates these goals with the demands of the overblown, often putrid domestic politics.

Why does Australia have a policy of offshore detention of unauthorised maritime arrivals? The purpose is to deny them access to our legal system and, ultimately, Australian residency. The rationale is that without the lure of resettlement in this country, people will not be motivated to board those leaky boats.

And that leaves more spaces in our humanitarian resettlement program which, as our major parties keep reminding us, is generous by international standards.

A corollary is that resettlement in another first-world country, like New Zealand or Canada, would also constitute a "pull factor", and so people should only be sent to unappealing, poor places such as Cambodia and Papua New Guinea.

Is actual cruelty also a part of the equation? Must life in detention on Nauru and Manus be unpleasant and punitive, to double down on the disincentives?

Surely not. To deliberately inflict psychological or physical pain on people who are guilty of no crime would be morally indefensible. No Australian government would do that. Would we?

Yet some of the language, and current government policy, implies it does. Throw in the potent perceived electoral lessons of Tampa and "children overboard" in 2001, rational political discussion becomes impossible.

And no one has yet explained why the government is unable to take action to heighten security on those two islands.

During the Howard government's final two terms, the Liberal party room contained a significant minority of MPs who agitated, with occasional success, for softening of policy. Then, after 2007, Labor ended offshore processing, abolished temporary protection visas and, while retaining mandatory detention, promised to process claims more quickly. Hardly "open borders", but packaged as such by people smugglers to restart their business model, it even, wretchedly, seems likely that the moderated language – assurances that people would be treated humanely – became part of the sales pitch.

The boats roared back, and in this Coalition government there are no asylum-seeker "mavericks" to be found. The argument is over; they all support harsh policies. And further inside the "base" the issue has become, as with global warming, totemic of the party's very identity. A prime minister weakened by a close re-election result has little room to move – even if he wanted to.

Meanwhile, many asylum-seeker supporters blithely suggest something called a "regional arrangement" which, with the bulk of asylum-seekers flying to Indonesia from the other side of the planet, with the specific aim of getting to Australia, doesn't stand the most fleeting scrutiny.

Unless the suggestion is that any displaced people around the world able to afford a flight to Jakarta will, if found to be refugees, automatically be resettled in Australia.

Earlier this month Frank Brennan, Tim Costello, Robert Manne and John Menadue penned "A solution to our refugee crisis" for Fairfax newspapers.

They believe the Coalition's boat turn-back policy, coupled with heightened cooperation with Indonesian authorities, is now sufficient to keep traffic at bay, and so those poor souls on Manus and Nauru can now be brought to Australia without risk of incentivising more arrivals. (The refugees anyway; they make no mention of the several hundred whose claims were rejected.)

That's a leap in faith – and contradicts a 2014 Menadue blog post titled "Tony Abbott did not stop the boats" which concluded that instead "The game-changer was Kevin Rudd's announcement of July 19, 2013 on no resettlement in Australia for boat arrivals".

But it's still probably worth a try even if it fails and another group of individuals ends up in offshore detention.

The alternative, letting them rot, is unthinkable.

Peter Brent is an adjunct fellow at Swinburne University.