The spread of gender theory is misleading so many Catholics that a high-level document may be required to correct the errors of the ideology, a Dutch cardinal said.
Cardinal Willem Eijk of Utrecht, Netherlands, said a papal encyclical or other magisterial document "might appear to be necessary" to counter the spread of the new theory that gender can be determined by personal choice rather than by biology.
He said even Catholic parents were beginning to accept that their own children can choose their genders partly because "they don't hear anything else."
The church, he said, now had an urgent duty to remind them of the truth of its teaching about the human body.
He told Catholic News Service in a Nov. 7 interview that Pope Benedict XVI and Pope Francis have addressed the subject within the past five years as each noted that the theory was taking root in Western societies.
"Perhaps a document only on this problem might be an urgent question," Cardinal Eijk said.
"It [gender theory] is spreading and spreading everywhere in the Western world, and we have to warn people," he said.
"From the point of moral theology, it's clear — you are not allowed to change your sex in this way," said the cardinal.
"It is like euthanasia and assisted suicide."