This Commandment has been continuously contradicted throughout the millennia. Today, as in the past, it is widely held that in certain circumstances killing is both just and necessary. Homicide is an anthropological constant of the human spirit, a bloody hallmark of our species: Cain ushers in biblical history by murdering Abel. But what exactly does Cain kill in Abel? The individual person, progeny according to Hebrew tradition, sacredness according to Christianity, the "naked life" of exterminations, or the mere biological operation in current end-of-life debates? Such questions represent the crucial bio-political, theological and scientific issues raised by this Commandment. Does the prohibition of murder enjoy an absolute status?

Adriana Cavarero teaches Political Philosophy at the University of Verona.

Angelo Scola, Patriarch of Venice since 2002 and a cardinal since 2003, used to teach Theology at the University of Freiburg and the Pontifical Lateran University.