"Ours is not a unitary country," Couillard told a special session of Ontario lawmakers. "I fight every day to keep it united. It's a federation that was built on the foundation of provinces and that's something we want to send as a message, because it's part of the fabric of the country."
A federation where regional and cultural differences are respected "will be the backbone of our future, and one of the building blocks of the prosperity we all want to leave to our children," added Couillard.
"When Ontario's economy is strong, all of Canada benefits," he said. "And when Quebec and Ontario work together to forge a strong economy, when they display imagination and dare to go even further, then everything becomes possible."
Quebec and Ontario account for more than 60 per cent of Canada's population and almost 60 per cent of its gross domestic product, he said.
"We are natural allies," said Couillard. "Central Canada is an economic force. It is a political force, and it is a force to be reckoned with for ensuring national prosperity."
The last premier from outside the province to address the Ontario legislature was Quebec's Jean Lesage in 1964, who predicted that government relations would shift from vertical, or federal to provincial, to horizontal, or province to province.
"This vision has been realized," Couillard said to cheers from all sides of the legislature and the packed public galleries. Former prime minister John Turner and former NDP premier and one-time federal Liberal leader Bob Rae were among the dignitaries attending Couillard's speech.
Speaking in both English and French, Couillard said Lesage and then-Ontario premier John Robarts fought to increase the role of the provinces in the federation.
Getting Quebec's distinct society recognized in the Canadian Constitution is still the province's ultimate goal, but it is willing to work with other provinces on a host of issues that they have in common for now, added Couillard.
"We have the same demands for many years, and probably the most central of them is to make sure that eventually — and it will happen — Quebec's distinct specific character is officially and formally recognized," he said.
Premier Kathleen Wynne praised Couillard for his willingness to partner with Ontario on climate change, inter-provincial trade and electricity sharing agreements, but she was non-committal on Quebec's Constitutional concerns.
"If there is a later conversation about the Constitution we will all take part in that, but there is a lot of other work for us to do," said Wynne. "It's not that I'm avoiding the (constitutional) discussion, but the reality is we are confronting challenges together, and we have to find solution to those challenges."
Couillard called Wynne's plan to join a cap-and-trade system under the Western Climate Initiative with Quebec "excellent news," and said his government expected to generate $3 billion by 2020 through its carbon market auctions.
"What I want to emphasize here is that putting a price on carbon is a logical choice," said Couillard. "Increasingly adopted here and abroad, it is also a choice that will yield concrete results."
Ontario, Quebec and California will create the largest carbon market in North America and "have good reasons to hope that others will follow suit," he added.
The two premiers have banded together to press Prime Minister Stephen Harper to take more action to deal with climate change, and raised the same environmental concerns about the proposed Energy East pipeline project.
"Ontario and Quebec are working together to build a stronger central Canada, and thereby a stronger Canada," Wynne said.
Couillard also said co-operation between the two Liberal governments is generating "promising leads" on expanding inter-provincial trade and growing the economy, and said Quebec wants strong relations with all provinces.
"The government I lead firmly believes that Quebec progresses when it seeks to unite rather than divide," he said. "When it participates rather than excluding itself. Above all, when it builds bridges with its partners in the federation rather than putting up walls."
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