His life is near its end. But until his life processes cease life is still present and cannot be taken except by due process. The Constitution protects life, not viability. Viability denotes the potential, not the actual. The law deals in what is, not in what may or may not be.
Viability is a function of vitality.
Vitality is life itself. Blackmun contradicted himself by using this term to set his standard of law. That is the dilemma Blackmun has posed for us as a result of his contradiction. Again, the Constitution protects life and its presence, not viability or potential. The obligation of the Court was to determine what it was dealing with in unequivocal terms.