Assume that, as sometimes happens, an infant has been born with massive and irreparable brain damage. The damage is so severe that the infant can never be any more than a "human vegetable," unable to talk, recognize people, act independently of others, or develop a sense of self-awareness. The parents of the infant, realizing that they cannot hope for any improvement in their child's condition and being in any case unwilling to spend, or ask the state to spend, the thousands of dollars that would be needed annually for proper care of the infant, ask the doctor to kill the infant painlessly.
Legally, the doctor should not kill the infant, and in this respect the law reflects the sanctity of life view. Yet people who would say this about the infant do not object to the killing of nonhuman animals. How can they justify their different judgments? Adult chimpanzees, dogs, pigs, and members of many other species far surpass the brain-damaged infant in their ability to relate to others, act independently, be self-aware, and any other capacity that could reasonably be said to give value to life. The only thing that distinguishes the infant from the animal, in the eyes of those who claim it has a "right to life," is that it is, biologically, a member of the species Homo sapiens. But to use this difference as the basis for granting a right to life to the infant and not to the other animals is, of course, pure speciesism. It is exactly the kind of arbitrary difference that the most crude and overt kind of racist uses in attempting to justify racial discrimination.