Animal Liberation Front (A.L.F.): Complete Diary Of Actions” is the first of its kind, and an important reference for any serious animal rights historian. Scientific laboratories, research institutions, fur farms and factory farms are just some of the types of organizations to be targeted by the ALF, often by destruction of property, animal rescue and undercover filming of the animal cruelty taking place. Further information: Animal rights §20th century: Increase in animal use; animal rights movement, Gary Francione, Tom Regan, Richard D. Ryder, and Peter Singer

ELF evolved out of Earth First!, an ardent environmentalist group founded, in its own words, "in response to a lethargic, compromising, and increasingly corporate environmental community." Dave Foreman, a former lobbyist for the Wilderness Society, and several other activists influenced by more militant organizations, founded Earth First! around 1980. Tatchell, Peter (29 January 2009). "The book that changed my life - Animal Liberation". The New Statesman. UK. Archived from the original on 26 August 2017 . Retrieved 23 December 2016. The book has also received a wide range of philosophical challenges to his formulation of animal rights. In a lengthy debate in Slate, published in 2001, Richard Posner wrote, among other things, that Singer failed to see the "radicalism of the ethical vision that powers [his] view on animals, an ethical vision that finds greater value in a healthy pig than in a profoundly intellectually challenged child, that commands inflicting a lesser pain on a human being to avert a greater pain to a dog, and that, provided only that a chimpanzee has 1 percent of the mental ability of a normal human being, would require the sacrifice of the human being to save 101 chimpanzees." Singer replied to and rejected this claim, engaging in a lengthy debate with Posner. [10] While Animal Liberation Now fortifies Singer’s earlier case, further objections will be forthcoming. Some animal advocates will be disconcerted that Singer, a utilitarian, theoretically approves of harmful animal experiments, albeit within narrow bounds. Although he opposes most current animal experimentation, Singer is open to condoning, for example, experiments on monkeys that substantially improve the lives of tens of thousands of people with Parkinson’s disease. Some advocates will feel that even these experiments violate animal rights. Despite these differences, the terms "animal liberation" and "animal rights" are generally used interchangeably.

Smaller factions include groups focused around faith-based animal rights theory and veganarchists, whose approach is characterized by a critique of capitalism on the grounds that it has led to mass nonhuman, human, and environmental exploitation. [4] [8] Since the 1970s, the Animal Liberation Front has been at the forefront of exposing animal exploitation and cruelty around the world. To understand the motivation of the Animal Liberation Front, it’s important to understand where the ALF came from and the people who set it on the path of direct action in the name of animal rights. The group combined environmental protection with a form of spirituality called "deep ecology," popularized by a Norwegian philosopher and mountain climber, Arne Naess. Members regarded their activities as not merely political but also spiritual. During the 1980s, Earth First! activists performed direct actions ranging from tree-sitting to tree spiking - hammering a long nail that can create shrapnel injuries when cut by logging tools such as a chainsaw. As Singer argues, such large-scale, profit-driven systems cannot treat animals humanely. Meanwhile, scientific research continues to show that animals, including farmed species, possess many mental capacities similar to those of humans. These capacities, as Charles Darwin recognised, include affection, grief, sympathy, memory, attention and curiosity.

Animal researchers at Wake Forest University in North Carolina were also targeted in February 2009. In a communiqué, the "Justice Department" claimed responsibility for mailing razor blades covered in rat poison to two scientists there and warned, "This is only the start…End the experiments on the primate captives or it only gets worse." The "Justice Department," an offshoot of Animal Liberation Front (ALF), the most active extreme animal rights movement in the country, injured several people using letter-bombs in the 1990s.January 2005: Harrison David Burrows was sentenced to 2 1/2 years in prison for his role in an arson at Ellsworth Farms, an animal husbandry building on the campus of Brigham Young University in Provo, Utah. Burrows, 18, pleaded guilty to destruction of property by fire. Burrows and co-defendant Joshua Stephen Demmitt, who earlier pleaded guilty to the same charge and received the same sentence, admitted setting the July 2004 fire on behalf of the Animal Liberation Front. Some forms of animal treatment, Singer tells us, have improved somewhat. Certain countries began to better regulate animal research as the animal rights movement gained steam in the 1980s. In response to activism and changes in public sentiment, the European Union banned testing of cosmetics on animals, and the US National Institutes of Health ended its support for harmful research on chimpanzees. In its early years, where they limited their activity to removing animals, damaging property and exposing cruelty, the Animal Liberation Front had garnered sympathy and support from the public, largely due to their non-violent stance. But as their actions became more militant and individual members started to choose more violent ways to achieve its objectives, the ALF started to become more isolated.