Pope Benedict XVI on Friday weighed in on a heated debate over gay marriage, saying same-sex unions called into question what it means to be "true men".
"In the fight for the family, the very notion of being – of what being human really means – is being called into question," Benedict said in Italian during an end-of-year speech.
While he did not specifically refer to gay marriage, it was a clear bid by the pontiff to block the spread of the legalisation of gay marriage which is gaining ground in the West. France, Britain and the United States are expected soon to join a dozen countries where homosexual couples can legally wed.
"The question of the family... is the question of what it means to be a man, and what it is necessary to do to be true men," Benedict said.
The pope spoke of the "falseness" of gender theories and cited at length France's chief Rabbi Gilles Bernheim, who has spoken out against gay marriage.
"Bernheim has shown in a very detailed and profoundly moving study that the attack we are currently experiencing on the true structure of the family, made up of father, mother, and child, goes much deeper," he said.
He cited feminist gender theorist Simone de Beauvoir's view to the effect that one is not born a woman, but one becomes so -- that sex was no longer an element of nature but a social role people chose for themselves.
"The profound falsehood of this theory and of the anthropological revolution contained within it is obvious," he said.
The defence of the family, Benedict said, "is about man himself. And it becomes clear that when God is denied, human dignity also disappears."
In an article for Britain's Financial Times newspaper on Thursday, the pontiff reminded the country's increasingly secular population the Church was not just concerned with morals, but also social issues.
"It is in the Gospel that Christians find inspiration for their daily lives and their involvement in worldly affairs -- be it in the Houses of Parliament or the Stock Exchange," the pope said in the article.
He also stressed the need for the Church to dialogue with atheists and agnostics who agree with the church's social codes.
He spoke of the possibility of forming an "alliance" based on a common respect for the "law of nature," in reference to the traditional marriage between a man and a woman.
On Monday, the Vatican's newspaper described laws on gay marriage as an attempt at a communist-like "utopia", a day after tens of thousands of demonstrators turned out in France to support legalising both marriages and adoption for gay couples.
France's parliament is to debate the government-backed "marriage for all" bill early next year.
With President Francois Hollande's Socialists enjoying a strong majority, the bill is expected to pass despite vehement opposition from the right and religious groups.