This being the first day back at school, Andrew Scheer was obliged to stand and tell the class what he'd done with his summer.

"Mr. Speaker, this summer I spent my time crossing the country talking to hard-working Canadians, job creators and entrepreneurs," Scheer reported.

"And I can tell the prime minister one very simple thing: they are not tax cheats," he said, turning to stare down Justin Trudeau.

Scheer's fellow Conservatives applauded.

The Conservative leader presumably did not mean to imply he had reviewed the tax returns of each and every person he spoke with this summer.

Rather, he meant to take issue with the Trudeau government's hotly contested implication that something is amiss in what the tax system allows.

"These are the people who mortgage their homes, who take an idea and create opportunities in their neighbourhood," Scheer ventured. "So my simple question to the prime minister is, why is he hurting the very people he claims he wants to help?"

Trudeau tax plan under fire in QP2:28

In response, the prime minister attempted to parse any misunderstanding.

"Mr. Speaker, there is no suggestion that any Canadians aren't following the rules," he said.

The Conservatives cried out in objection.

"The problem is, the rules we have currently favour the wealthy over the middle class," Trudeau continued. "We have a system right now that allows wealthy Canadians to use private corporations to pay lower tax rates than middle class Canadians.

"That's ... not ... right."

Scheer would stand another 10 times to query the prime minister about the government's proposals to change the tax rules for incorporated entities and a succession of Conservatives would use the rest of the Official Opposition's opportunities to pursue the same topic.

Nary a word would be said about Omar Khadr and his multimillion-dollar government settlement, this summer's previous outrage. Perhaps if Khadr had incorporated himself over the summer, the Conservatives would still be interested in his case.

It's possible both sides are actually happier to be fighting about tax reform. The Conservatives because lots of people hate taxes and the Liberals because lots of people like the idea that taxes should be applied fairly.

The mechanic and the doctor

Scheer would eventually narrow his concern to the plight of the Canadian mechanic.

"Right now, a mechanic can save in these investments to save up for a new purchase, which will allow her to hire another worker," Scheer explained. "The Liberal plan will tax those investments twice. That will kill any opportunity for her to expand and hire more workers."

The Conservative struck an angry, dimple-less expression as he sat down.

Ideally, this would be followed by a full accounting of how many mechanics would be impacted by the Liberal changes and how precisely they would be made markedly worse off.

And that would be followed by a discussion of whether mechanics deserve to have access to savings mechanisms — sprinkling income among family members, saving money within their business — that are not available to individuals who are not incorporated.

Question Period 20170918

Conservative Leader Andrew Scheer says he spent his summer 'crossing the country talking to hard-working Canadians, job creators and entrepreneurs' who feel targeted by the Liberals' proposed changes to the tax system. (Sean Kilpatrick/Canadian Press)

But question period is not the place for such details.

Trudeau would eventually land on his own example.

"Mr. Speaker, the member opposite, and indeed the entire opposition, has been going around the country, telling every doctor that they meet that they stand with them," Trudeau said.

The Conservatives seemed unsure how to react to this comment, whether to applaud themselves or object to the suggestion.

"That they will defend their rights to pay lower taxes than nurses that work alongside those doctors," Trudeau continued. "We don't think that's fair."

Luckily for Trudeau, apparently not all doctors are mad at him.

'Job creators' and the 'wealthiest'

But if the Liberals can show that mechanics will be no worse off, they might yet escape this.

In the meantime, Scheer will claim to be defending "job creators." Trudeau will claim his intention is to ensure the "wealthiest" are not advantaged over the "middle class."

Every so often Monday the NDP interjected with a question about nuclear disarmament or the bridge to Detroit.

Trudeau challenged Scheer to explain whether a future Conservative government would reverse the Liberal changes, a challenge that would land harder if the Liberals had settled on a complete set of specific proposals. At this point, there is only a "consultation document."

Scheer suggested Trudeau's Liberals are only pursuing these changes in order to balance the budget, a charge that would make more sense if a significant amount of tax revenue was in play. At the moment, the new measures would barely put a dent in the deficit.

Scheer worried about the "the entrepreneur who has to self-fund her maternity leave because she does not have a government-funded plan." But that might actually sound like an argument for extending government benefits.

Both Trudeau and Scheer suggested the other doesn't understand what's being proposed.

The actual math might eventually catch up to one or both of them. But, for the moment, both would seem to sense they have a defining moment at hand.