From Wesley J. Smith at First Things:
Most people understand the word “death” to mean the end of biological life or, as Merriam-Webster defines it, “a permanent cessation of all vital functions.” But now an influential cadre of utilitarian bioethicists wants to redefine it to include a subjective and sociologically based meaning. Their purpose isn’t greater scientific accuracy. Rather, by making “death” malleable, they hope to open the door further to treating indisputably living human beings as if they were cadavers.
Legally, human death is declared when medical testing discerns the irreversible cessation of one of two biological functions that must work for a human being to be considered an integrated functioning organism. The first is the cardio/pulmonary function, the irreversible cessation of which is sometimes called “heart death.” The other is the brain; irreversible total brain failure, or the permanent cessation of the brain and each of its constituent parts acting as a brain, is popularly known as “brain death.” (Brain death is controversial in some quarters, but I won’t go into that here.)
The redefiners contend that these approaches are too constraining. What also matters, they claim, is the exhibition of characteristics that they claim earn an individual the status of “person.” Let’s call this “personhood theory”—the belief that moral value, and even death, can be determined by the presence or permanent absence of mental capacities such as self-awareness. In this view, those who, through injury or illness, have lost the ability to express personhood should be considered dead or, at least, as good as dead. More.
This dovetails with the growing belief that human beings are not special
To understand what it looks like, check out Euthanasia: Estimating death rates in Canada