Lifton

Of the five identifiable steps by which the Nazis carried out the principle of "life unworthy of life," coercive sterilization was the first. There followed the killing of "impaired" children in hospitals; and then the killing of "impaired" adults, mostly collected from mental hospitals, in centers especially equipped with carbon monoxide gas. This project was extended (in the same killing centers) to "impaired" inmates of concentration and extermination camps and, finally, to mass killings in the extermination camps themselves.

Robert Jay Lifton