You can read Clark’s essay in full below.

The Right Honourable Joe Clark: A country like Canada is about both geography and state of mind. Our immense geography was confirmed when Sir John A. Macdonald's railway connected the physical nation from sea to sea. The state of mind -- the sense of being one people, one community of communities -- has always been more elusive.

John Diefenbaker -- that passionate, difficult, courageous, Western populist -- enlarged both our sense of Canada's geography, and the ranks of Canadians who felt they truly belonged to this country. He did that imperfectly -- building on what his life had taught him, and failing where he would not trust the different experience of others.

Geographically, his emphasis on northern development opened our imagination to our North. We began to think like a nation whose reach was from sea to sea to Northern sea -- and, therefore, whose reach was greater than it had seemed before.

Similarly, his policies of regional development gave rural and Western and Atlantic Canada a sense that they were as important a part of the future of their country as the Golden Triangle.

But his real and rare accomplishment is that he opened the sense of being Canadian to people who had felt shut out before.

The theory of democracy is that we all have equal opportunity. The facts are different. Before John Diefenbaker became prime minister, no woman had served in the cabinet of Canada. Nor had any Canadian whose origins were other than English or French. Status Indians -- our "first citizens" -- were denied the right to vote.

He changed all that. Ellen Fairclough took her place in his first cabinet. Michael Starr, a Canadian of Ukrainian origin, served there with her. Status Indians received the right to vote in 1960.

He tore down barriers. He introduced simultaneous translation to the House of Commons, so unilingual English- and French-speaking MPs could understand one another. He passed the first Canadian Bill of Rights. He was a leader in the Commonwealth Conference that expelled the then-apartheid regime of South Africa.

And beyond those specific acts, he made ordinary people believe he was their champion.

Political leaders before him had been austere, remote. They walked with power, a little above the people. Not John Diefenbaker. One way or another -- loved or reviled -- he became personal to most of the people of Canada. He mainstreeted through life, giving courage and connection to those who admired him, often infuriating those who did not.

His personal experience affected him profoundly, for better and for worse. His attitudes and understanding were shaped on the Prairie, in Parliament, and in the courts. No one with that background and perspective had ever been prime minister before.

The courts and Parliament were adversarial. His national renown, as a lawyer, was as the skillful defender of individual and minority rights. He fought the system and, often, he won.

In his later years in the House of Commons, he spoke frequently of the camaraderie among members of Parliament of different parties. But those were not the characteristics that let him dominate that chamber. He was an advocate, an adversary, a singular force.

He had the gift to express consensus, when he found it, eloquently. But it was not in his nature, nor his experience, to build consensus, as Macdonald and Wilfrid Laurier did. He came from a different place.

Remember, his Prairie was the frontier, in the 1920s and '30s. The people he served and knew lived on the edge; their world was framed by the hope of the homesteader, and the despair of the dust bowl, and the Depression. It was not a place for theorists, not a place of wealth. His training and profession gave him a privileged standing.

But his ordinary practice was as a people's lawyer, dealing with hard cases, not a corporate lawyer, creating enterprises. He saw systems fail and people suffer -- and he was with the people.

Moreover, he won office as prime minister suddenly, and almost personally. The more familiar part of John Diefenbaker's electoral story is his determination and persistence. Before he squeaked into Parliament in 1940, he lost every federal and provincial election he contested. But once he became party leader, in late 1956, his victories were swift, in 1957 and '58. He could be forgiven for believing that they owed much more to his own skill than to his party's policy or organization or alliances.

The Diefenbaker government changed profoundly the nation's priorities. It brought to them a Western Canadian experience, and an outsider's perspective. Those two characteristics are not synonymous. The outsider was clearly a part of John Diefenbaker's makeup -- the defence lawyer, the man sensitive to slights, the person who sympathized with those in need.

But the regional innovations of his government -- the Agricultural Rehabilitation and Development Act, northern development, investment in Atlantic Canada, the wheat sales to China -- built on positive pan-Canadian instincts. They were national policies, not regional, motivated by growth not grievance. They were designed to complete the work Macdonald began -- to have national policies that reflected the interests of the whole nation.

John Diefenbaker was far from faultless as prime minister. Many of his lessons are of traps we should avoid.

He was suspicious and distrustful. His interest in the economy was casual. He did not understand -- nor, tragically, seek to understand -- the gathering transformations in Quebec.

Against that must rank:

His government's profound changes in our systems of justice and social justice, from national hospital insurance to the creation of Emmett Hall's royal commission on health care;

Mr. Diefenbaker's consistent courage in the face of American pressures;

His government's ingenuity in making our federation work; and

His unquestioned success in opening our country to so many more of our own citizens.

If detachment is a prerequisite to evaluating prime ministers, then I am the wrong person to write about John Diefenbaker. I was 17 when I first heard him speak, in the community centre of my little town. I watched his eyes literally blaze when he spoke of his "vision of a new and greater Canada."

"Visions" get undone by Bomarc missiles, and American presidents, and the other hard realities of life. But the value of "visions" is the context they set, the far horizons they inspire.

I had learned about Champlain and Cartier, Macdonald and Laurier, Louis Riel and Joseph Howe. But they were from some other story.

They had little to do with my small Alberta town, until John Diefenbaker put them together.

He brought me into my country. He made it matter to be a Canadian. In different ways, he made Canada matter for thousands of Canadians. He opened the nation to itself, and let us see our possibilities.