A little background:
Singer: In Chapter 4 we saw that the fact that a being is a human being, in the sense of a member of the species Homo sapiens, is not relevant to the wrongness of killing it; it is, rather, characteristics like rationality, autonomy, and self-consciousness that make a difference. Infants lack these characteristics. Killing them, therefore, cannot be equated with killing normal human beings, or any other self-conscious beings.
Singer: Rigorous adherence to a single principle has a way of hoisting one by one’s own petard. Singer’s mother suffers from severe Alzheimer’s disease, and so she no longer qualifies as a person by his own standards, yet he spends considerable sums on her care. This apparent contradiction of his principles has not gone unnoticed by the media. When I asked him about it during our interview at his Manhattan apartment in late July, he sighed and explained that he is not the only person who is involved in making decisions about his mother (he has a sister). He did say that if he were solely responsible, his mother might not be alive today.