Timeline of ideas

In the dialogue Euthyphro he formulated the dilemma: is something good because the gods approve of it, or do the gods approve of it because it is good?

Founder of virtue ethics; he saw animals as existing for human use, within a natural hierarchy.

Held that death is not an evil: "where death is, we are not." The collection discusses and rejects this view.

Formulated the symmetry argument: we do not regret the time before we were born, so we should not regret the time after death.

A contractualist: morality arises from an agreement among self-interested people to avoid the war of all against all.

Defined a person by a consciousness that extends over time, an idea used in the debate on identity and the harm of death.

Held that only rational beings are ends in themselves; our duties regarding animals would be indirect (cruelty to them would make us cruel to humans). Contemporary Kantians such as Korsgaard argue that the theory itself implies considering animals directly.

Wrote that the question is not whether animals can reason or talk, but whether they can suffer.

A pioneer: in Moral Inquiries (1824) he advocated not using animal products and was already discussing helping animals against natural harms such as predation.

In the essay "Nature" he shows that "natural" does not mean "good": nature routinely does things we would condemn in humans.

Proposed "reverence for life": every living being deserves respect, an idea that inspired biocentrism.

Proposed prima facie duties (fidelity, non-maleficence, beneficence, etc.); he denied that animals have rights, although he accepted duties toward them.

In A Sand County Almanac (1949) he formulated the land ethic: a thing is right when it tends to preserve the integrity, stability and beauty of the biotic community. The value lies in the whole, not in individual animals.

Attributes intrinsic value to nature and to the diversity of life as a whole, not only to sentient beings.

In Man and Mouse (1984) he defends animal experimentation for its medical benefits to humans.

In Animals and Why They Matter (1983) she criticizes the treatment of animals but argues that preferring one's own species is a natural bond, and to some extent a legitimate one.

Proposed two-level utilitarianism: intuitive rules for everyday life and critical calculation for hard cases.

In A Theory of Justice (1971) he proposed the veil of ignorance; he himself excluded animals from justice, but the impartiality test he proposed is used to include them.

In Respect for Nature (1986) he defends biocentrism: every living being has a "good of its own" and inherent value, whether sentient animals, plants or microorganisms.

In Animal Rights and Moral Philosophy (2005) he argues that Kant's categorical imperative, properly understood, requires treating all sentient beings as ends in themselves.

In The Rights of Animals and Unborn Generations (1974) he argues that only those who have interests can have rights, and that animals have interests but plants do not.

One of the founders of the ethics of care, centered on concrete relationships.

Placed the preservation of nature above the good of humans and other animals, going so far as to advocate a drastic, authoritarian reduction of the human population. He is cited as an extreme example of holistic environmentalism.

In Thinking, Fast and Slow (2011) he describes the biases and heuristics that distort our judgments, the basis of Volume X.

Argued that biological diversity has value in itself and that conservation should protect species and ecosystems.

In The Case for Animal Rights (1983) he argues that every "subject-of-a-life" has inherent value and rights, which rules out using them as mere resources.

In Anarchy, State, and Utopia (1974) he described the position "Kantianism for people, utilitarianism for animals," which the collection criticizes.

In Putting Humans First (2004) he argues that humans have moral priority because they are moral agents, and that animals have no rights.

In Interests and Rights (1980) he denied that animals have interests in the moral sense because they lack language; he defended animal experimentation.

In Created from Animals (1990) he defends "moral individualism": how we treat someone should depend on the characteristics of each individual, not on species.

In ¡Vivan los animales! (1998) he criticizes cruelty to animals but allows hierarchies of consideration.

In Reasons and Persons (1984) he analyzed personal identity, psychological connectedness and population ethics, topics used in the debate on the harm of death and on future beings.

Argued that animals have interests and a "telos" (a nature of their own) that must be respected, and discussed animal experimentation.

In Animal Rights and Wrongs (1996) he claims that rights belong only to members of the moral community, who are capable of duties; to animals we owe only a certain kindness.

Proposed a multi-criteria view of moral status that gives animals a lower status than persons.

Showed empathy and prosocial behavior in other primates, discussing the origins of morality.

Grounded utilitarianism in impartial choice under uncertainty: what we would choose without knowing who we would be.

In Animal Liberation (1975) he popularized the term "speciesism" and the principle of equal consideration of interests: suffering of equal intensity counts equally, no matter whose it is.

Argues that morality is an agreement among those who can cooperate and retaliate; since animals cannot, they would have no rights (Animal Rights, 1977).

In The Moral Status of Animals (1977) and in his article on "the problem of predation" he discusses whether we would have to intervene in nature.

In Duty and the Beast (1978) he accepts duties toward animals, but of lesser weight than duties toward humans.

Discussed the moral basis of vegetarianism and argued that it is reasonable to give more weight to humans.

In On Being Morally Considerable (1978) he argues that being alive, not being sentient, is the criterion for moral consideration.

Argued that only those who can claim something for themselves can have rights, which would exclude animals.

Argued that Rawls's original position, applied consistently, should include animals (Of Beasts, Persons and the Original Position, 1979).

Defends a holistic ethics: the good of the biotic community (ecosystems and species) is the ultimate criterion of value. In Animal Liberation: A Triangular Affair (1980) he went as far as to claim that this good can outweigh that of individuals, humans included; he later softened his position.

In Death (1970) he argues that death is an evil of deprivation; in What Is It Like to Be a Bat? (1974) he discusses the subjectivity of experience.

In Death, Misfortune and Species Inequality (1981) she argues that death is not a misfortune for animals because they supposedly lack categorical desires about their own future.

In Faking Nature (1982) he argues that original nature has a value that restored nature does not recover.

In The Priority of Human Interests (1983) he defends the priority of human interests on the basis of social ties and closeness.

Writes on animal and environmental ethics, including zoos and climate change.

In Morals, Reason and Animals (1987) he defends animal liberation and argues that, in principle, we would have reasons to prevent predation when possible.

In Babies and Beasts (1997) he analyzes the history of the argument from species overlap.

Works on theories of well-being and defends a form of sufficientarianism based on compassion.

In Against Liberation (1991), drawing on Wittgenstein, he denies that animals have a mental life rich enough to carry the same moral weight as humans.

In Eating Meat and Eating People (1978) she argues that our morality is shaped by relationships and by the idea of "fellow human beings," not by capacities; she accepts compassion for animals, but not equality.

In In Nature's Interests? (1998) he argues that all living beings have "biological interests," although he gives priority to the interests of conscious beings.

Argues that death is a harm because it deprives a person of the good they would have had.

In The Animals Issue (1992) he maintains that animals have no direct moral status, since they cannot take part in a moral contract; our obligations toward them would be only indirect.

In The New Ecological Order (1992) he criticizes deep ecology and antispeciesism, defending a humanism in which only humans have full dignity.

Criticizes restoration of and intervention in nature as forms of human domination over it.

Grounds the value of nature in its aesthetic qualities.

In Policing Nature (2003) he argues that, in principle, we have reasons to reduce predation when it is feasible.

Formulated discourse ethics: valid norms are those that everyone affected would accept in a free dialogue.

In Animal Liberation and Environmental Ethics: Bad Marriage, Quick Divorce (1984) he argues that animal advocacy and environmentalism are incompatible.

Defends a basis for equality between species (A Basis for (Interspecies) Equality, 1993).

A theorist of egalitarianism and of how to compare outcomes (Inequality, 1993; Rethinking the Good, 2012).

Defends the value of "wild" nature and discusses exotic species and respect for the autonomy of natural processes.

In The Sexual Politics of Meat (1990) she links the oppression of women to that of animals; she is associated with the ethics of care.

Works on theories of well-being based on informed desires.

Defends the abolitionist approach: the central problem is that animals are property; he proposes veganism as a moral baseline and criticizes welfarist reforms.

In Beyond Prejudice (1995) she develops the argument from "marginal cases": if humans without certain capacities count, animals without them count too.

Estimates the number of fish caught and farmed each year worldwide.

Develops the ethics of care as applied to animals, centered on empathy and attention to suffering.

Criticizes the idealization of nature and argues that antispeciesism must also take wild animals into account.

In Slaughterhouse (1997) she gathered testimony from slaughterhouse workers about what happens to the animals.

With Niall Shanks, in Brute Science (1996), he questions the scientific validity of animal experimentation.

Author of Normative Ethics (1998), used in the collection to explain the "focal point" of theories. In How to Count Animals (2019) he defends a hierarchical view: animals matter, but less than persons.

Proposes a "concentric circles" theory: stronger obligations toward those who are closer to us, within a pluralistic environmental ethics.

Applies Rawls's contractualism to animals: behind the veil of ignorance we would not know whether we would be human, so justice would include animals.

Author of the entry on the concept of discrimination in the Encyclopedia of Applied Ethics.

In Darwinian Dominion (1999) he argues that favoring one's own species is natural and morally justified by evolution.

Coined the term "speciesism" in 1970 and later proposed "painism": what matters is each individual's pain.

In The Animal Question (2001) she extends human rights theory to animals; with Singer, she organized the Great Ape Project.

Discusses the "predation problem" at the intersection of environmental ethics and animal ethics.

Researches cognition and sentience in invertebrates, especially octopuses.

In The Ethics of Killing (2002) he proposes that the harm of death depends on "time-relative interests" and on psychological connectedness with the future, which would make death less serious for many animals. He has also written about the moral problem of predation.

Systematized the argument from species overlap (The Argument from Species Overlap, 2002).

Defends moral arguments for veganism and against the use of animals.

Works at the intersection of animal ethics and environmental ethics, including the management of wild animals.

Popularized the concept of existential risk and has written about artificial superintelligence.

In The Philosopher's Dog (2002) he explores the relationship between humans and animals, defending a view that sets apart the moral place of humans.

Studies indicators of sentience and of well-being in many species.

Analyzes environmentalist programs that kill animals considered "out of place," such as introduced species.

A pioneering researcher on pain in fish.

In Fellow Creatures (2018) she argues, starting from Kant, that animals are also ends in themselves, against the reading that only indirect duties would apply to them.

Argues that human status depends on the "species norm" (The Species-Norm Account of Human Status, 2005).

Has published scientific opinions on the sentience and welfare of animals used in production.

Argues, from virtue ethics, that cruelty and indifference toward animals are vices.

Extends the capabilities approach to animals: each should be able to flourish according to its own form of life (Justice for Animals, 2023).

Defended utilitarianism applied to animals and was a pioneer in proposing cultivated meat as a way to reduce suffering.

One of the leading authors on speciesism and on the suffering of wild animals; argues that natural harms matter just as much as those caused by humans.

Author of Ética & Animais (2006), an introduction to the debate in Portuguese.

Author of Essays on Reducing Suffering; estimates the numbers of animals (especially insects) and advocates reducing the suffering of wild animals and the risks of future suffering.

Defends prioritarianism (benefits are worth more to those who are worse off) and has written about the harm of death.

In Taking Animals Seriously (1996) he defends serious consideration for animals, but allows different weights depending on mental complexity, especially regarding the harm of death.

Discusses animal rights in the face of predation and the duty of assistance.

In The Hedonistic Imperative (1995) he proposes using biotechnology to abolish the suffering of all sentient beings, including in nature.

Author of Animal Ethics in the Wild (2023); argues that we have reasons to help wild animals harmed by natural processes.

In a debate with Singer, he argued that it is legitimate to give preference to humans and to trust the intuition that humans matter more.

Advocates "compassionate conservation," which tries to reconcile conservation with the good of each animal.

In his dissertation (2013) he argued for the enormous importance of shaping the distant future.

Applies virtue ethics to the animal question, showing that it too condemns harming animals unnecessarily.

Defends suffering-focused ethics and concern for wild animals and for risks of future suffering.

Writes about the ethics of intervening in nature on behalf of animals.

Has written about s-risks and about the asymmetry between suffering and happiness.

Studies the animal advocacy movement and defends an abolitionist and intersectional approach.

Author of an introduction to theories of well-being (2016).

With Colin Klein, he argued that insects have brain structures capable of subjective experience (2016).

Author of Avoiding the Worst (2022); the collection's main reference on s-risks (risks of suffering on an astronomical scale) and how to prevent them.

In The End of Animal Farming (2018) he analyzes strategies for ending animal agriculture, including food technology and institutional change.

In the works cited, he defends equal consideration for all sentient beings, including wild animals who are victims of natural processes.

In Towards Welfare Biology (1995) he proposed "welfare biology" and argued that suffering prevails in nature because of mass reproduction.

Author of Suffering-Focused Ethics (2020); argues for prioritizing the reduction of intense suffering, including in the future.

In What We Owe the Future (2022) he defends longtermism: giving great weight to how our decisions affect the distant future.

Coauthor, with MacAskill, of The Case for Strong Longtermism.

In Wild Animal Ethics (2021) he advocates research-based interventions to reduce the suffering of wild animals.

Works on the well-being of wild animals and on the feasibility of interventions to help them.

Led the report that led the United Kingdom to recognize the sentience of octopuses, squid, crabs and lobsters (2021); defends the precautionary principle.