Cardinal Francis George told Chicago-area Catholics that the passage of a same-sex marriage law in the state would be "acting against the common good of society."
"This proposed legislation will have long-term consequences because laws teach; they tell us what is socially acceptable and what is not, and most people conform to the dictates of their respective society, at least in the short run," he wrote in a letter Tuesday.
The letter, sent to all archdiocesan pastors to be distributed in parish bulletins, was also signed by Chicago's six auxiliary bishops and posted online on the website of the Illinois Catholic Conference, www.ilcatholic.org.
The letter was issued the day before a group of Illinois lawmakers introduced the "Religious Freedom and Marriage Fairness Act," which would make all state laws that are "applicable to marriage apply equally to marriages of same-sex and different-sex couples and their children."
The cardinal said the bill's title was deceptive and "ignores basic truths."
He said the Catholic church is not "anti-gay" because it "welcomes everyone, respects each one personally and gives to each the spiritual means necessary to convert to God's ways and maintain friendship with Christ."
He pointed out that "marriage comes to us from nature" and said it is "physically impossible for two men or two women to consummate a marriage, even when they share a deep friendship or love," which indicates that "marriage is what nature tells us it is and that the state cannot change natural marriage."
If this legislation passes, the cardinal warned that those who "continue to distinguish between genuine marital union and same-sex arrangements will be regarded in law as discriminatory, the equivalent of bigots."
He also stressed that if society ignores in law "the natural complementary of man and woman in creation, then the natural family is undermined. Our individual lives become artificial constructs protected by civil 'rights' that destroy natural rights. Human dignity and human rights are then reduced to the whims of political majorities. When the ways of nature and nature's God conflict with civil law, society is in danger."
George also urged Catholics to stay informed on the issue and contact their state legislators about it.
In his column in the Chicago New World for the first week of January, the cardinal said the proposed legislation could have "enormous consequences for everyone."
He said "some religious people have framed their acceptance of this proposed law as an exemplification of compassion, justice and inclusion. As attitudes, these sentiments have been used to justify everything from eugenics to euthanasia. If religion is to be more than sentiment, the moral content of these words has to be filled in from the truths of what human reason understands and God has revealed."
The cardinal noted that "same-sex unions are incompatible" with church teaching but he also noted that the Catholic church in the Chicago Archdiocese has "consistently condemned violence or hatred of homosexually oriented men and women. Good pastoral practice encourages families to accept their children, no matter their sexual orientation, and not break relationships with them."