Moral circle expansion is an increase over time in the number and type of entities given moral consideration. [1] The general idea of moral inclusion was discussed by ancient philosophers and since the 19th century has inspired social movements related to human rights and animal rights. Especially in relation to animal rights, the philosopher Peter Singer has written about the subject since the 1970s, and since 2017 so has the think tank Sentience Institute, part of the 21st-century effective altruism movement. There is significant debate on whether humanity actually has an expanding moral circle, considering topics such as the lack of a uniform border of growing moral consideration and the disconnect between people's moral attitudes and their behavior. Research into the phenomenon is ongoing.
The moral circle was discussed as early as the 2nd century by Stoic philosopher Hierocles, who described in On Appropriate Acts the concentric social circles of a human being, for whom duty to the innermost circle was strongest. [1] The concept was developed more fully by William Lecky in his 1869 work History of European morals from Augustus to Charlemagne. [1]
Edward Payson Evans, an early advocate for animal rights, published Evolutional Ethics and Animal Psychology in 1897. He argued that humans need to move past anthropocentric conceptions that view humans as fundamentally different and separate to all other beings and that, as a result, humans have no moral obligations toward them. [2] The utilitarian philosopher and animal rights advocate J. Howard Moore argued for a sentientist philosophy in his 1906 book The Universal Kinship , asserting that humans should care about all sentient life based on shared evolutionary kinship:
The partially emancipated human being who extends his moral sentiments to all the members of his own species, but denies to all other species the justice and humanity he accords to his own, is making on a larger scale the same ethical mess of it as the savage. The only consistent attitude, since Darwin established the unity of life (and the attitude we shall assume, if we ever become really civilised), is the attitude of universal gentleness and humanity. [3]
The concept was notably developed by the utilitarian philosopher Peter Singer in his 1981 book The Expanding Circle , which is titled after the concept of moral circle expansion. [4] This book sets out a common theory of the expanding circle: humans started by only valuing those most similar to themselves, such as their family or social group, but then humans began to value other residents of their nation and finally humanity as a whole; the same process of expansion is now taking place with respect to animal rights. Singer wrote in the book that "The only justifiable stopping place for the expansion of altruism is the point at which all whose welfare can be affected by our actions are included within the circle of altruism." Singer also references the expanding circle in some of his other works. [5] [6]
Moral circle expansion has also been addressed by some later writers, whose definitions of it may not be exactly the same as Singer's. Robert Wright responds to Singer with a more critical conception in his 1994 book The Moral Animal :
The most cynical explanation of why so many sages have urged an expanded moral compass is the one set out near the beginning of this chapter: a large compass expands the power of the sages doing the urging. [7]
T. J. Kasperbauer's 2018 book Subhuman defines the expansion of the moral circle in reference to an increase both in the number of things considered moral patients and how many kinds of things are considered moral patients. Kasperbauer also adds in that this degree of consideration for things newly in the moral circle must be large enough to be important. [8]
The effective altruism movement, particularly the Sentience Institute, regularly discusses moral circle expansion as a part of its philosophy. [9] Launched in 2017 as a spinoff of the Effective Altruism Foundation, the Sentience Institute describes itself as a "think tank dedicated to the expansion of humanity's moral circle." [10] Its website provides a more detailed model of the circle itself, including concentric circles: the innermost represents full moral consideration, the outermost represents minimal consideration, and some entities fall entirely outside the circles. They additionally distinguish between a moral circle for attitudes and one for actions, and between a societal moral circle and an individual one. [11] Moral circle expansion as a concept per se was developed in a 2021 paper in the journal Futures entitled "Moral Circle Expansion: A Promising Strategy to Impact the Far Future" by Sentience Institute co-founder Jacy Reese Anthis and philosopher Eze Paez. [1]
Philosopher Jeff Sebo's 2025 book, The Moral Circle , argues for expanding the scope of ethics to include not only humans but also animals, insects, artificial intelligence, and microbes. He critiques the concept of human exceptionalism, examining how human practices such as factory farming, captivity, and technological development often fail to consider the interests of nonhuman entities. Sebo explores these ideas through case studies on captive elephants, farmed insects, and the ethical issues surrounding the creation of digital minds. The book calls for a reconsideration of ethical responsibilities and advocates for systemic changes to create a more inclusive and equitable future. [12]
Many different entities have arguably entered, and sometimes exited, the moral circle at some point during human history: [1] [5]
Any given entity or group of entities may enter the moral circle at different times for different people. This current expansion of the moral circle to include animals is referred to by Kasperbauer as an expansion from a circle of all humans to a circle of all sentient things. [8] Sigal Samuel has also suggested that plants, nature and robots may be beginning to enter the moral circle. [5] Anthis and Paez refer to the circle as a "multidimensional gradient" that ranges from wishing harm on someone to caring about someone even more than one's self. [1]
Kasperbauer and others point out that it is not entirely clear whether the actual conditions of animals used for food or scientific research are improving, despite claims that they are entering the moral circle. [1] [8] A related criticism is that religion gave some animals a protected status that they no longer have, so they have experienced moral circle contraction. [13] Other suggested groups that have left the moral circle or gone farther from the center are gods and ancestors, whereas infants and fetus have had different moral standings in different societies. [14]
The idea of a moral circle has also been criticized as based in Western morality and so not reflecting the diversity of moral views found in the rest of the world, including concepts such as ahimsa that give greater value to animals than found in Western culture. [1] [5]
The question of what causes the expansion of the moral circle is an active topic of debate among the idea's proponents. [1] [8] The inclusion of animals within the moral circle has been credited to various traits that some animals possess, such as being cute or intelligent or having relationships with humans. By contrast, Peter Singer has emphasized the importance of rationality among humans as a way in which the moral circle is expanded. [5] Another theory is that moral circle expansion is related to climbing Maslow's hierarchy of needs and so being able to focus on others to a greater extent once more personal needs have been fulfilled. [5] The relationship between laws and what people consider to be part of their moral circle is also a subject of inquiry. [1]
The concept of a moral circle and its expansion, including the causes of its expansion, has been the subject of much recent work in the field of moral psychology. [1] Psychologists have found significant biases in how people think of their moral circle based on the way that the question is framed, [15] as well as that people tend to give more moral consideration to high-sentience animals than to low-sentience animals, more moral consideration to animals than to plants, and more moral consideration to plants than to "villains" such as murderers. [16] The Moral Expansiveness Scale (MES), developed by Charlie R. Crimston, is a psychological measure of altruism that developed from thinking about moral circle expansion. [16] [17]
Speciesism is a term used in philosophy regarding the treatment of individuals of different species. The term has several different definitions. Some specifically define speciesism as discrimination or unjustified treatment based on an individual's species membership, while others define it as differential treatment without regard to whether the treatment is justified or not. Richard D. Ryder, who coined the term, defined it as "a prejudice or attitude of bias in favour of the interests of members of one's own species and against those of members of other species". Speciesism results in the belief that humans have the right to use non-human animals in exploitative ways which is pervasive in the modern society. Studies from 2015 and 2019 suggest that people who support animal exploitation also tend to have intersectional bias that encapsulates and endorses racist, sexist, and other prejudicial views, which furthers the beliefs in human supremacy and group dominance to justify systems of inequality and oppression.
Moral agency is an individual's ability to make moral choices based on some notion of right and wrong and to be held accountable for these actions. A moral agent is "a being who is capable of acting with reference to right and wrong."
In ethical philosophy, altruism is an ethical doctrine that holds that the moral value of an individual's actions depends solely on the impact of those actions on other individuals, regardless of the consequences for the actor. James Fieser states the altruist dictum as:
"An action is morally right if the consequences of that action are more favorable than unfavorable to everyone except the agent."
Animal rights is the philosophy according to which many or all sentient animals have moral worth independent of their utility to humans, and that their most basic interests—such as avoiding suffering—should be afforded the same consideration as similar interests of human beings. The argument from marginal cases is often used to reach this conclusion. This argument holds that if marginal human beings such as infants, senile people, and the cognitively disabled are granted moral status and negative rights, then nonhuman animals must be granted the same moral consideration, since animals do not lack any known morally relevant characteristic that marginal-case humans have.
Animal ethics is a branch of ethics which examines human-animal relationships, the moral consideration of animals and how nonhuman animals ought to be treated. The subject matter includes animal rights, animal welfare, animal law, speciesism, animal cognition, wildlife conservation, wild animal suffering, the moral status of nonhuman animals, the concept of nonhuman personhood, human exceptionalism, the history of animal use, and theories of justice. Several different theoretical approaches have been proposed to examine this field, in accordance with the different theories currently defended in moral and political philosophy. There is no theory which is completely accepted due to the differing understandings of what is meant by the term ethics; however, there are theories that are more widely accepted by society such as animal rights and utilitarianism.
The intrinsic value of a human or any other sentient animal comes from within itself. It is the value it places on its own existence. Intrinsic value exists wherever there are beings that value themselves.
Sentientism is an ethical view that places sentient individuals at the center of moral concern. It holds that both humans and other sentient individuals have interests that must be considered. Gradualist sentientism attributes moral consideration relatively to the degree of sentience.
Effective altruism (EA) is a 21st-century philosophical and social movement that advocates impartially calculating benefits and prioritizing causes to provide the greatest good. It is motivated by "using evidence and reason to figure out how to benefit others as much as possible, and taking action on that basis". People who pursue the goals of effective altruism, who are sometimes called effective altruists, follow a variety of approaches proposed by the movement, such as donating to selected charities and choosing careers with the aim of maximizing positive impact. The movement has achieved significant popularity outside of academia, spurring the creation of university-based institutes, research centers, advisory organizations and charities, which, collectively, have donated several hundreds of millions of dollars.
Jacy Reese Anthis is an American social scientist, writer and co-founder of the Sentience Institute with Kelly Witwicki. He previously worked as a Senior Fellow at Sentience Politics, and before that at Animal Charity Evaluators as chair of the board of directors, then as a full-time researcher.
Moral progress refers to improvement in concepts such as moral beliefs and practices experienced on a societal scale. Michele Moody-Adams noted that "moral progress in belief involves deepening our grasp of existing moral concepts, while moral progress in practices involves realizing deepened moral understandings in behavior or social institutions".
The Expanding Circle: Ethics and Sociobiology is a 1981 book by Peter Singer bridging the topics of sociobiology and ethics.
The Sentience Institute (SI) is an American interdisciplinary think tank that aims to expand humanity's moral circle. It was founded by Jacy Reese Anthis and Kelly Anthis in June 2017 and has published research reports on social movements, morality, animal advocacy and digital sentience.
John Howard Moore was an American zoologist, philosopher, educator, and social reformer. He was best known for his advocacy of ethical vegetarianism and his pioneering role in the animal rights movement, both deeply influenced by his ethical interpretation of Darwin's theory of evolution. Moore's most influential work, The Universal Kinship (1906), introduced a sentiocentric philosophy he called the doctrine of Universal Kinship, arguing that the ethical treatment of animals, rooted in the Golden Rule, is essential for human ethical evolution, urging humans to extend their moral considerations to all sentient beings, based on their shared physical and mental evolutionary kinship.
The Universal Kinship is a 1906 book by American zoologist and philosopher J. Howard Moore. In the book, Moore advocates for the doctrine of Universal Kinship, a secular sentiocentric philosophy, which mandates the ethical consideration and treatment of all sentient beings based on Darwinian principles of shared evolutionary kinship, and a universal application of the Golden Rule, a challenge to existing anthropocentric hierarchies and ethics. The book built on arguments Moore first made in Better-World Philosophy, published in 1899, and was followed by The New Ethics in 1907. The Universal Kinship was endorsed by a number of contemporary figures including Henry S. Salt, Mark Twain and Jack London, Eugene V. Debs and Mona Caird.
The relationship between animal ethics and environmental ethics concerns the differing ethical consideration of individual nonhuman animals—particularly those living in spaces outside of direct human control—and conceptual entities such as species, populations and ecosystems. The intersection of these two fields is a prominent component of vegan discourse.
The ethics of uncertain sentience refers to questions surrounding the treatment of and moral obligations towards individuals whose sentience—the capacity to subjectively sense and feel—and resulting ability to experience pain is uncertain; the topic has been particularly discussed within the field of animal ethics, with the precautionary principle frequently invoked in response.
Catia Faria is a Portuguese moral philosopher and activist for animal rights and feminism. She is assistant professor in Applied Ethics at the Complutense University of Madrid, and is a board member of the UPF-Centre for Animal Ethics. Faria specialises in normative and applied ethics, especially focusing on how they apply to the moral consideration of non-human animals. In 2022, she published her first book, Animal Ethics in the Wild: Wild Animal Suffering and Intervention in Nature.
Evolutional Ethics and Animal Psychology is an 1897 book by the American scholar and early animal rights advocate Edward Payson Evans. It is an in-depth exploration of the intersection between ethical theory and animal psychology, with a particular focus on the rights of animals and the moral obligations humans have toward them.
Moral patienthood is the state of being eligible for moral consideration by a moral agent. In other words, the morality of an action can depend on how it affects or relates to moral patients.
The Moral Circle: Who Matters, What Matters, and Why is a 2025 book by philosopher Jeff Sebo. In the book, Sebo calls for a fundamental shift in ethics, advocating for the expansion of humanity's moral circle to include not just humans, but also animals, insects, AI systems, and even microbes. He critiques human exceptionalism, emphasizing how human current treatment of nonhumans—whether through factory farming, captivity, or technological development—often neglects their interests. Through case studies on captive elephants, farmed insects, and the ethical dilemmas of creating digital minds, Sebo explores how expanding the moral circle could transform society. As humanity continues to reshape the world, he argues for a rethinking of human ethical responsibilities and the implementation of systemic changes to create a more just and inclusive future.
{{cite book}}
: CS1 maint: date and year (link){{cite book}}
: CS1 maint: location missing publisher (link)