ROME -- Pope Benedict XVI on Tuesday cancelled a speech at Rome's La Sapienza University in the face of protests led by scientists opposed to a high-profile visit by the head of the Catholic Church to a secular setting.
"Following the well-noted controversy of recent days ... it was considered appropriate to postpone the event," which had been set for Thursday, a Vatican communiqué said, in the first such cancellation in the face of hostility since the pope's election in April 2005.
Many scientists fault the intellectual, conservative and tradition-minded pope for a series of positions he has taken that they say subordinate science and reason to faith.
The protest against the visit was spearheaded by physicist Marcello Cini, a professor emeritus of La Sapienza, who wrote to rector Renato Guarini complaining of an "incredible violation" of the university's autonomy.
Sixty-seven professors and researchers of the sprawling university's physics department, as well as radical students, joined in the call for the pope to stay away on Thursday, the start of the university's academic year.
Students opposed to the visit kicked off "an anti-clergy week" on Monday by showing a film on Galileo, the 17th-century physicist who ran afoul of Church doctrine by insisting that the Earth orbits the Sun.
Italian Prime Minister Romano Prodi condemned the professors and students for "intolerance" towards the pontiff, and renewed the invitation for Benedict to visit the public university.
"I condemn the acts, statements and attitudes that provoked unacceptable tension and a climate that does not honor Italy's traditions of civility and tolerance," Prodi said, according to the ANSA news agency.
Signatories to the letter protesting the planned visit recalled a 1990 speech in which the pope, then Cardinal Joseph Ratzinger and head of the Roman Catholic Church's doctrinal watchdog, seemed to justify the Inquisition' s verdict against Galileo in 1633.
In the speech, Ratzinger quoted an Austrian philosopher who said the ruling was "rational and just".
He concluded with the remark: "The faith does not grow from resentment and the rejection of rationality, but from its fundamental affirmation, and from being rooted in a still greater form of reason."
One of the protesting professors, Carlo Cosmelli, told AFP: "Since the conviction of Galileo ... physicists are especially sensitive over interference by the Catholic Church in the scientific domain."
The pope -- who also faces criticism for perceived interference in Italian political and social affairs -- "has made more and more remarks on the theme of the necessary subordination of science to faith," Cosmelli said.
The controversy is the most heated since the pope's speech of September 2006 at Renesburg University when he inflamed the Muslim world with remarks -- also quoting someone else, in that case a Byzantine emperor -- appearing to link Islam with violence.
Cosmelli said the Galileo remarks were "just as problematic. "
Cini also recalled a colloquium on Darwin held by Benedict in September 2006 in which the "intelligent design" movement was given precedence over the theory of evolution.
"The Church can no longer use pyres or corporal punishment," Cini said in the communist daily Il Manifesto. "Today it uses the Enlightenment' s God of Reason as a Trojan horse to enter the citadel of scientific knowledge."
The scientists' revolt, initially discreet, snowballed after radical students took up the cause.
On Tuesday they briefly occupied the rector's offices seeking the right to demonstrate on Thursday.
Benedict's predecessor John Paul II, who visited the school only once, in April 1991, also faced strident heckling and whistles by small groups of protesters.
Cini said of Benedict on Thursday: "By canceling, he is playing the victim, which is very intelligent. It will be a pretext for accusing us of refusing dialogue."