has given a quick whois
in his writeup on Peter Singer, but I feel that a little more of an explanation for his striking and seemingly contradictory views is in order.
Singer's point of view stems from two basic premises. First, he is a self-described preference utilitarian, meaning that he finds the greatest moral good to be in the satisfaction of the most preferences or desires (this is a slight refinement from early utilitarianism which emphasized happiness).
Second, he holds there is a fundamental difference between the two senses in which we generally use the term human. The first simply refers to "a member of the species homo sapiens" whereas the second refers to a person. While being a member of the species homo sapiens is a straightforward matter of genetics and not really open to debate or interpretation, personhood requires self-awareness and the capacity for reason. For Singer, the difference between the two is crucial. A member of the species homo sapiens, like any other animal, has the right to be free from undue suffering, but a person, in contrast, has all of what we traditionally refer to as human rights.
Singer's passionate vegetarianism stems largely from the first premise of preference utilitarianism. Because non-human animals are just as capable of suffering as humans, he holds that there is no justification for causing them to suffer (not to mention die) simply because we enjoy the taste of their flesh.
Regarding euthanasia, because preference utilitarianism enshrines the desires of the individual as being of the highest moral concern, Singer is led to the conclusion that a person of sound mind who truly wishes to die (generally, the terminally and painfully ill) should be allowed to do so.
Where Singer runs into controversy is in his views relating to homo sapiens that are not people. This includes not only the brain dead (which is commonly accepted) but the terminally comatose, under the justification that while parts of the hindbrain may still be keeping the terminally comatose alive in the traditional sense, the parts of the brain that give personality (and ultimately bestow personhood) are dead in these cases. Once the personality is dead, the person is dead and all that is left is a body.
Similarly, the category of homo sapiens that are not people includes not only the embryo and the fetus (which are commonly accepted) but also the newborn infant. He agrees with conservatives that there is no rational defense of the position that a seven-month-old fetus can ethically be aborted while a three-months-premature newborn must be saved by any means possible. Unlike conservatives, he places the crucial dividing line not at conception but self-awareness. Self-awareness generally comes around age two or so but, he argues, in issues of morality it is best to be very cautious so it would be sensible to grant legal personhood (including the right to life) at perhaps one month. It should be clear that, so far as I know, Singer advocates only that, as with abortion, parents should have the right to infanticide, not that it should be a matter of policy in cases of disability.
Whether one agrees or disagrees with Peter Singer's views, it must be conceded that, unlike many ethicists who repeat generally accepted wisdom despite the bundle of contradictions it implies, Singer has a clear ethical vision and is not afraid to see it through to unconventional conclusions.