In a speech Feb. 24 to more than 350 Catholic medical professionals, the Pope said so-called "designer embryos" represent one of many contemporary attacks on human life. The attacks have increased to the point that the Christian conscience has been lulled, and even good people sometimes seem paralysed in the face of collective social pressure against the right to life, he said.

The Pope listed a number of ways in which human life is threatened in poorer nations today, including pressure to legalize abortion, new forms of chemical abortion introduced under the pretext of "reproductive health," and the continuing politics of demographic control.

In richer countries, he said, biotechnological engineering aims to establish "subtle and extensive methods of eugenics in the obsessive search for the 'perfect child,' through artificial procreation and various forms of diagnosis that allow selection." He said this kind of genetic selection is part of "a new wave of discrimination" aimed at the unborn.

The Pope did not name specific countries, but on the same day it was reported that the British government would allow scientists to genetically modify embryos for research purposes – which many see as a step closer to the genetic breeding of babies.

The Pope also warned against increasing pressure to legalize euthanasia. In addition to such direct attacks on life, he said, efforts are multiplying to legalize "alternative" forms of co-habitation that are closed to procreation.

"In these situations the conscience, at times overcome by the means of collective pressure, does not demonstrate sufficient vigilance about the seriousness of what is at stake," he said.

The Christian is called to mobilize continually against attacks on human life, because it is the most fundamental of all human rights, he said. That is why the formation of a true and correct conscience is such an essential task for parents, educators and pastors.

But he said conscience formation today is hindered in many ways, particularly by popular attitudes of tolerance that mistrust the very capacity of reason to perceive the truth.

"Thus the conscience, which is an act of reason that aims at the truth of things, ceases to be a light and instead becomes a simple background on which the mass-media society projects contradictory images and impulses," he said.

In order to reawaken the conscience as an eloquent and clear voice, the Pope said, the church needs to work at the family and parish level so that young people are educated in basic values and church teachings. Lay Catholics should know that, particularly on human life issues, they need to welcome the church's teaching, he said.