Prime Minister Malcolm Turnbull found himself in trouble in a Sky News interview. Picture: Dean Lewins Source: AAP

ONE of Prime Minister Malcolm Turnbull’s greatest dangers this election is his unblinking, unrelenting, unmovable faith in logic.

It got him into trouble during the week in a Sky News interview and it no doubt will do so again.

This is politics Prime Minister — election politics at that.

Logic gets jostled to the back of the campaign bus by the bully-boys of scare campaigns, half-truths and misrepresentations dispatched by both sides.

The issue this week was the 10-year costing of the company tax cuts proposed in Tuesday night’s Budget.

Mr Turnbull was asked how much this would take from revenue, in light of estimates of $55 billion from a private economist.

It was a perfectly valid question and the Prime Minister gave a perfectly unhelpful answer. In essence, he didn’t know.

In fact, nobody knew until Treasury secretary John Fraser told an estimates committee hearing on Friday — after Treasurer Scott Morrison had telephoned Mr Fraser on Thursday evening suggesting a number would be handy.

The number, by the way, is $48.2 billion. Happy?

Secretary of the Treasury John Fraser told an estimates committee hearing how much company tax cuts would take from revenue.Source:News Corp Australia

Mr Turnbull didn’t just look like a dill, he looked like a hypocrite, and that is the critical political take from this episode. But let’s go to the core of the matter.

It is a feature of the past few years of political contest that parties don’t just account for measures over the four years itemised in the Budget but offer — or demand — a reckoning for a full decade.

Voters are being asked to believe that major party figures who have not been able to stick to a single leader for a three-year term will know with acceptable precision the outcome of tax and spending policies per 10 years.

We’ve had four prime ministers in three years of swirling changes and somehow we expect these same people to know to a decimal point what the economy will be doing in 2026.

It is absurd. There are so many unpredictable influences and methods of reckoning that any attempt would at best be a highly educated guess, no matter the good will and skill behind it.

And the politicians are to blame for suggesting it can be done, and for the bickering over abstruse calculations beyond the ken of any normal person, and beyond direct relevance to many voter concerns.

The Coalition did it to Labor by discrediting it’s so-called Gonski scheme for education funding, arguing there was no money for it beyond the four-year accounting of the original proposal.

And this week the Coalition claimed there was a $20 billion black hole in Labor’s tobacco excise policy — costed by the independent Parliamentary Budget Office — over 10 years.

So there was the Prime Minister having the same standard put to him: How much would the Budget’s proposal to cut company tax to 25 per cent cost revenue over 10 years?

Malcolm Turnbull was interviewed by David Speers on Sky News.Source:Supplied

Malcolm Turnbull at times tends to respond as if he’s at a symposium of like minds discussing generalised situations, and this interview was one of them.

He knew a definitive figure was not available.

Logic said it didn’t and couldn’t exist.

And anyway, the Budget papers had a nice graph showing the general direction of all manger of things in the years ahead.

And this is what happened:

DAVID SPEERS: I’m asking about the 10 year — you put a ten year plan

in the Budget, what’s the cost?

TURNBULL: All of those costs are taken into account in the medium term

outlook and it’s set out.

SPEERS: What is the cost?

TURNBULL: Well, it’s set out there. You can see the outcome.

SPEERS: I can’t see it in the Budget?

TURNBULL: You can.

SPEERS: What the 10 year figure is?

TURNBULL: You can see it there. The Budget outcome, the balance over

to 26/27 is set out there on page 3-11 on Budget Paper 1.

SPEERS: And what’s the figure?

TURNBULL: Well you can see it there. It shows the budget returning to balance.

SPEERS: Doesn’t say what the cost is though, not the Budget returning

to balance. What’s the cost of your company tax plan?

TURNBULL: The cost of the plan is set out in the medium term outlook

and shows the Budget returning to balance.

And so on.

Eventually, Mr Turnbull went to the friendly warmth of logic.

“Budget papers set out a medium term outlook and they do that every Budget. And they make assumptions about tax rates, they make assumptions about GDP, they make assumptions about commodity prices,” he said.

“And of course, the further out they go ... you forecast, there is more uncertainty.

“One of the certain assumptions that is in the medium term outlook is of course the policy which will be legislated to reduce company tax, down to 25 per cent over 10 years.”

So essentially, 10-year outlooks are in most cases rubbish. They are just political jousting sticks.

And one of them just clouted the Prime Minister.