Animal rights proceeds from the notion that nonhuman animals possess, as people do, a set of basic inalienable rights -- to life, liberty, and the pursuit of happiness -- by virtue of their status as living, sentient beings. Some advocates of this view would grant such rights only to animals such as primates possessing relatively high capacities for "thought" and learned response. Other animal rights activists make no such distinction and would extend these rights to all living creatures. The common thread linking all such advocates is their conviction that it is unjust for man to regard animals as property, and, by extension, to use animals to serve his needs or desires in terms of food, entertainment, cosmetics, clothing, scientific testing, etc.

The concept of animal rights is different from animal welfare, whose advocates oppose the infliction of unnecessary suffering on animals without assigning specific "rights" to them. The classic expression of animal welfare and man's obligation, as the pinnacle of creation, to exercise a humane stewardship of the animals below (and to some degree dependent on him) is Matthew Scully's Dominion.

The two most prominent academic proponents of animal rights today are Peter Singer and Thomas Regan. Regarded as the bible of the animal rights movement, Singer's 1975 book Animal Liberation argues from the axiom that man should grant respect and moral worth to animals not on the basis of their intelligence or any particular cognitive skill, but rather because of their ability to experience pain and suffering. Singer brands any denial of animals' basic "rights" a form of discrimination, comparable to racism and sexism, called "speciesism." He deems it wrong to assign greater inherent value to human beings than to any other form of animal life - be it a bird, a fish, or a mouse. He rejects the Biblical notion that mankind is nature's steward and master; that humans have souls and animals do not; and that people are uniquely made in the image of God. "All three [of the foregoing axioms] taken together do have a very negative influence on the way in which we think about animals," Singer says, explaining that his self-identified mission is to challenge "this superiority of human beings."

Notwithstanding his opposition to the killing of animals, Singer believes that human parents should be legally permitted to kill a "severely disabled" infant up to 28 days after its birth if they deem the baby's life not worth living. "There are some circumstances," he says, ". . . where the newborn baby is severely disabled and where the parents think that it's better that that child should not live, when killing the newborn baby is not at all wrong."

Thomas Regan's position on animals differs somewhat from Singer's. Regan asserts that because the basic moral rights of humans are grounded in their possession of certain cognitive abilities, the higher animals that possess similar abilities ought to be granted the same basic moral rights as humans. He does not, however, call for extending those rights to every form of animal life.

Those who oppose the concept of animal rights argue that animals are not entitled to such rights because they are incapable of entering into a social contract, making moral choices, or understanding what rights are -- and because nature "is red in tooth and claw." According to the philosopher Roger Scruton, because only human beings have duties, "[t]he corollary is inescapable: we alone have rights." Michigan University philosophy professor Carl Cohen elaborates on this theme: "Only in a community of beings capable of self-restricting moral judgments can the concept of a right be correctly invoked." Robert Bidinotto, a writer on environmental issues, notes the philosophical contradictions in the animal rights worldview: "Strict observance of animal rights forbids even direct protection of people and their values against nature's many predators. Losses to people are acceptable . . . losses to animals are not. Logically then, beavers may change the flow of streams, but Man must not. Locusts may denude hundreds of miles of plant life . . . but Man must not. Cougars may eat sheep and chickens, but Man must not."

Those who advocate animal rights also tend to oppose, and often boycott, a number of industries that use animals; these include factory farming, the slaughter of animals, and the production of clothing made from animal skins. Moreover, they refuse to use products such as cosmetics, pharmaceuticals, or certain inks or dyes known to contain animal byproducts. Nor will they purchase products containing ingredients that have been tested on animals.

A growing number of animal rights activists engage in sometimes violent direct action -- such as the covert removal of animals from facilities that use them; the damage of property at such facilities in order to cause financial loss; or the threat of reprisal agaainst animal experimenters or others involved in the use of animals. People for the Ethical Treatment of Animals (PETA) was the trailblazer for this movement, popularizing such tactics as dumping buckets of fake blood on people's fur coats, or on the clothing and property of meat-manufacturing executives. Another prominent group to engage in illegal activities is the Animal Liberation Front (ALF), which candidly advocates vandalism, sabotage, and arson "to bring about animal liberation." The ALF was officially added to the FBI's list of domestic terrorist organizations in 1987, and has caused tens of millions of dollars in property damage over the years.