For the churches representing the majority of Canadian Christians, legalization of same-sex marriage will be a sign of the end of Christendom, the 1,700-year-old notion that has defined government in the Western world as devoted to the enforcement of Christian values, says one of Canada's leading theologians.

Those churches will be left feeling marginalized by the state -- a state they will no longer see as an expression of a Christian point of view and fulfilling certain Christian ideals, said Christopher Lind, director of the Toronto School of Theology, the federation of theological colleges affiliated with the University of Toronto.

It explains why a rope of fear runs through the churches' legal submissions to the Supreme Court, where hearings begin Wednesday on the constitutionality of the government's intention to authorize same-sex marriage.

There is fear that if, as widely expected, the court rules in favour of same-sex marriage and Parliament passes enabling legislation, churches will face persecution and discrimination in Canadian society for holding fast to the belief that God ordained marriage only for heterosexual couples.

From Roman Catholics and evangelical Protestants to Mormons, Muslims and Seventh Day Adventists among others, religious groups are also apprehensive that they may be stripped of their charitable status and other state benefits, penalized by public institutions, branded as hate-mongers and forced into accepting the legitimacy of same-sex unions.

It is the same fear that political scientists and theologians identify as driving the powerful conservative religious right in the United States -- a conviction that liberal, secular society is bent on erasing religion from public life.

But whether a redefined marriage law will ignite decades of political conflict -- as happened in America after the U.S. Supreme Court legalized abortion in 1973 with the case of Roe vs. Wade -- is what one conservative Anglican priest terms "a sociological Pandora's box."

"I doubt that anyone knows the potential fallout," said Rev. Ed Hird, rector of St. Simon's Anglican Church in North Vancouver, one of a dozen Greater Vancouver Anglican congregations in rebellion against their bishop for approving church blessings of same-sex unions.

"I do know biblically oriented Christians are not going to roll over and play dead. This would mean an abandonment of their core value of the final supremacy of holy Scripture."

Bruce Clemenger, president of the Evangelical Fellowship of Canada -- representing more than three million Canadians through 130 affiliated denominations, ministry organizations and educational institutions -- says the redefinition of marriage in Canada would cause conservative Christians to feel stripped of public language with which to express their values on marriage.

"We will have lost the [public] language to be able to describe something that's very meaningful within a religious tradition. How will parents impart their values to their children . . . in a society where their definition of marriage is seen to be discriminatory?"

He said the issue for conservative religious communities will be to advance the definition and substance of pluralism in Canada, to where "you have a plurality of public languages and options and choices that people can promote."

Charles McVety, president of Toronto's evangelical Canada Christian College, illustrated the loss of public language by describing the reaction to an e-mail he sent recently to members of Ontario's Conservative Party, urging them not to vote for John Tory as leader because he supported same-sex marriage. "The venom that came back. . . . People calling me an effing homophobe," he said. "You're demonized."

Snapshot of views

"Marriage is a benchmark by which Canadian society names the everyday development of love and intimacy between a couple . . . Restricting the definition of marriage to opposite-sex couples questions the capacity of gays and lesbians to develop love and intimacy, undermining their human dignity and reinforcing prejudicial attitudes and even promoting violence."

-- United Church of Canada

"By requiring [Canadians] to treat homosexual sexual practices as good, it will lead to intolerance of those who teach and espouse the opposite view which, in turn, will have wide-ranging negative consequences for freedom of religion and conscience."

-- Canadian Conference of Catholic Bishops

"Same-sex couples can and do live in long-term, caring, loving and conjugal relationships -- including those involving the rearing of children. Denying same-sex couples the choice of having their unions legally recognized as marriages perpetuates the view that they are not capable of forming intimate relationships of economic interdependence, and thus same-sex relationships are not worthy of the same respect and recognition as opposite-sex relationships."

-- Federal Department of Justice

"The companionate model of marriage advanced by the A-G Canada is troublingly over-inclusive. For example, the arguments made in favour of same-sex marriage can also be made in recognition of polygamy and polyandry. The definition of marriage advanced by A-G Canada is so broad that it risks depriving 'marriage' of any real meaning in the longer term and, in a perverse way, risks denying the advocates of same-sex marriage the social validation they seek."

-- Attorney-General of Alberta