Peter Singer: Changing Lives Through Practical Ethics

The 20th Anniversary of UNESCO’s World Philosophy Day is an apt moment for reflection on the value of philosophy. I am honoured to have been asked to contribute to this occasion.  Throughout my career, my focus has always been on the areas of philosophy that we can use to answer questions about how we should live and on the social and political structures in which we live with others.  In this essay, I will keep my gaze on what I know best: ethics, or moral philosophy, and in particular, that part of ethics that seeks to answer questions we face in our lives, in other words, practical ethics. Without in any way denying that there is value in other, more abstract fields of philosophy, it is with practical ethics that the value of philosophy can most clearly be seen.

My central point can be stated in just three words: ethics changes lives. I know of no other academic discipline that can do this as fundamentally, and as positively, as ethics. By thinking philosophically about ethics, we are more likely to make well-reasoned ethical judgments. Well-reasoned ethical judgments lead to better decisions. Better decisions lead to actions that are more ethical than the actions we might otherwise perform, if we had not tried to reach well-reasoned ethical judgments.  A life in which ethics plays a key role is a different, and better, life than one in which ethics plays only a minor role, or no role at all. 

We need to think philosophically about ethics, because our intuitive moral judgments may lead us astray.  These judgment reflect a variety of past influences. Often they are the feelings that helped our ancestors—social mammals, living in small groups—to survive, reproduce, and rear our offspring to independence. Such feelings include care for members of our community, but sometimes also include indifference, or even outright hostility, to others who look, speak, or act differently from those in our group. Because groups are often more likely to succeed if those in them have many children, we may also have strongly negative attitudes to sexual acts that do not lead to reproduction, including masturbation and homosexual acts. In a later era, religious teachings may reinforce these evolutionary tendencies, and make them more difficult to change, even when changing circumstances make them undesirable or positively harmful          .

We can recognize and condemn the racist and sexist moral biases of our ancestors but be blind to our own moral biases. To give an example: one such bias, I have argued in my books Animal Liberation (1975) and Animal Liberation Now (2023), is our readiness to attribute a higher moral status to all members of our own species than we do to any nonhuman animal, even if the member of our own species lacks the cognitive capacities of the animal. Compare, for example, the protection given to all humans—even anencephalic infants, who have no awareness and usually die within weeks of birth—but denied to nonhuman animals. To remove the heart of an anencephalic infant in order to transplant it into another infant with a lethal heart defect could lead to a charge of murder, while a physician who removed the heart of a pig for the same purpose would, if the procedure were successful, receive accolades.  But is this difference defensible, or is it, like racism or sexism, a bias that we have inherited from our ancestors?  I will not further argue this point here, because that would be too great a distraction from the main point of this article – I offer the example only to show that without careful thought and reasoning, we may not be acting as ethically as we think we are.

What is Practical Ethics?

Practical ethics (sometimes referred to as applied ethics) discusses a wide variety of practical questions. Some of these have given rise to specialized fields within the broad area of practical ethics. Here are some examples:

Poverty and Affluence

More than a billion people are affluent—that is, after meeting all their basic needs, they have money to spend on luxuries. At the same time, nearly 700 million people are living in extreme poverty. (As defined by the World Bank, a person is in extreme poverty if they have insufficient income to reliably meet their needs, such as for food, shelter, and basic health care.) There are effective charities helping people in extreme poverty, but they lack the resources to help all of them. In this situation, what are the obligations of the affluent to help those in extreme poverty?

Animal Ethics

What is the moral status of animals? We may care about the companion animals we have in our homes, but we treat vast numbers of other vertebrate animals as commodities. Worldwide, more than 200 billion vertebrate animals are raised for food each year, almost all of them crowded into what are essentially factories for converting cheap grain, soybeans, or fishmeal into higher-priced animal flesh, eggs, or milk—with the difference that the machines for doing the conversion are sentient beings. Is there a reason why it is acceptable to treat nonhuman animals in ways that it would obviously be wrong to treat any human being? Or is this, as already suggested, an example of a prejudice that is akin to the racism that many white people once thought justified enslaving people of another race?

Environmental Ethics

There are many reasons to care about the natural environment, including its importance for our own survival and the quality of our own life. But what is the value of non-sentient nature, such as plants, rivers, and ecosystems? Is it important to prevent the extinction of rare species, even if they do not play an important role in preservation of our own lives?

Climate Ethics

Gases emitted from our use of fossil fuels and from the large number of ruminant animals we raise are changing the climate of our planet in ways that are already contributing to lethal heatwaves, storms, floods, and droughts. If unchecked, these emissions will cause sea levels to rise, create hundreds of millions of climate refugees, and could make much of the planet unsuitable for human life. In a world of sovereign countries, these facts give rise to new ethical questions: How can we decide on the responsibilities of each country—with different levels of greenhouse gas emissions, both past and present—to reduce their emissions? Is this a question only for governments to consider, or ought individuals reduce the emissions for which they are personally responsible?

Bioethics

As medicine and the biomedical sciences advance, we face new ethical issues including:

• How far should we go in prolonging life, given that we can keep patients alive beyond the point at which this ceases to be a benefit to them?
• In an era in which it is possible to keep the heart beating and the blood circulating when the brain has irreversibly ceased to function, how should we define death
• Whether we are living in “normal” times or in a pandemic, medical resources are always limited. How should we allocate them?
• What limits should we place on biomedical research on human subjects, and on nonhuman animals?

We can now enable couples to produce multiple human embryos in vitro, and then screen them to select the embryo with the best prospect of turning out to be the child they desire. We are also developing the ability to modify the genes of an embryo so that a couple could have a child with capacities beyond those inherent in their own genes. Should we permit this knowledge to be used, and if so, under what constraints?

AI and Ethics

The rapid progress of artificial intelligence (AI) has led to a surge of interest in AI ethics. The issues discussed range from the prospect of AI putting many people out of work, and what we might do about that, through the choices to be made in programming the AI that will control self-driving cars, to the risk of superintelligent AI becoming our master and bringing about the extinction of our species.  In addition, we may one day face an AI that could itself be a sentient being.  If so, what moral status will it have?

Practical Ethics as the Cutting Edge of Ethics

If the point of ethics is to change lives, then practical ethics is its cutting edge. Philosophers working in ethics have made important contributions to all of the areas just mentioned, and to other practical ethical questions as well. In the field of global poverty, for example, the effective altruism movement, which has its roots in moral philosophy, has inspired many people to donate more, and more effectively, thu saving or improving the lives of millions of people.

Something similar can be said of the modern animal movement. As sociologists James Jasper and Dorothy Nelkin observed in The Animal Rights Crusade: The Growth of a Moral Protest (1992): “Philosophers served as midwives of the animal rights movement in the late 1970s.”

Does Ethics Really Make a Difference?

I mentioned earlier the assumption that making better ethical judgments will lead to better decisions, both individually and collectively, and hence to more ethical actions. To complete my argument for the view that the point of moral philosophy is to change lives, I need to ask whether there is any evidence that moral philosophy really can change lives.

In teaching ethics, I have had many students who have changed their minds about the ethical issues we have discussed in our classes. For some of them that change has led them to change their lives in important ways, including their choice of career, what they eat, and what they do with the money they earn. Others who have never been my students email me to say that my writings, or talks I have given, have led them to become vegetarian or vegan, to increase what they donate to charity, to start a new organization, or even in one or two cases, to donate a kidney to a stranger. This has led me to believe that teaching and writing ethics does make a difference.

In 2017, Eric Schwitzgebel challenged me to test that belief. Eric, together with Joshua Rust, had previously studied the moral behavior of professors specializing in ethics and found that, in eight different areas, they did not behave better than philosophy professors not specializing in ethics, or than professors in departments other than philosophy. If specializing in ethics, and teaching it, did not make professors behave more ethically, then it would be surprising if merely taking a class in ethics had more impact. Eric offered me an opportunity to test the impact of an ethics class on eating meat. He taught a large introductory ethics class at the University of California, Riverside. The students in the class also participated in small group discussions. His idea was to discuss the ethics of eating meat in half of these groups—randomly selected—and discuss a different topic in the other groups, which would function as a control, to eliminate any factors that might affect the meat consumption of all students, irrespective of whether they were in the groups that discussed the ethics of eating meat. The obvious problem that such a study design faces is following up on the eating practices of the students. One could ask the students to keep a journal recording what they ate, but would such reports be honest? Eric had a better idea. Most of the students he teaches eat at the university cafeteria, and use their student ID cards to pay for their meals. With the cooperation of the cafeteria management—and, of course, the approval of the university’s research ethics committee—he would be able to identify what the students ordered, and whether it included meat. He invited me to join him and another philosopher, Brad Cokelet, in designing a study to test whether the students who discussed the ethics of eating meat would order less meat from the cafeteria.

The study involved 1,143 students. Half the students were required to read a philosophical article defending vegetarianism, followed by a small group discussion with the option of watching a video advocating avoiding meat. The other half were a control group. They received similar materials and discussion on donating to help people in poverty. From the cafeteria, we obtained data on nearly 6,000 food purchases from 476 students. The purchases were identified with students who had, or had not, read and discussed the ethics of eating meat, but the data we received were made anonymous so that we could not identify any named student’s purchases. To Eric’s surprise, the result was a statistically significant decline, from 52% to 45%, in meat purchases among students in the meat ethics group, and the lower rate of meat purchases was maintained for a few weeks after the class. There was no change in the level of meat purchases in the charitable giving group (and we had no way of discovering whether these students gave more to charity).

Our study was, as far as we have been able to discover, the first properly controlled investigation, in the real world and not in a laboratory setting, of the impact of university-level philosophy classes on student behavior. The decline in meat-eating was not dramatic, but it is sufficient to show that moral philosophy in the classroom can change what students eat.

So it seems clear that practical ethics really can change lives. This is important, because such a change contributes to making the world a better place.  In fact, this improvement is not only because people who act more ethically improve the lives of the people, or other sentient beings, affected by their actions, but also because several studies have shown that people who act ethically, and live for a purpose, are likely to live happier and more fulfilling lives than those who do not.*

References

Jasper, James and Dorothy Nelkin The Animal Rights Crusade: The Growth of a Moral Protest, Free Press, New York, 1992.

Schwitzgebel, Eric, Brad Cokelet and Peter Singer, “Do ethics classes influence student behavior? Case study: Teaching the ethics of eating meat.” Cognition (October 2020).

Schwitzgebel, Eric, Brad Cokelet and Peter Singer, “Students eat less meat after studying meat ethics.” Review of Philosophy and Psychology (November 2021).

Schwitzgebel, Eric and Joshua Rust, “The moral behavior of ethics professors: Relationships among self-reported behavior, expressed normative attitude, and directly observed behavior.” Philosophical Psychology 27(3), (2013), 293–327.

Singer, Peter, Animal Liberation, New York Review of Books/Random House, New York, 1975.

Singer, Peter, Animal Liberation Now, Harper Perennial, New York, 2023.

*This essay is adapted from Peter Singer, “Changing Lives,” in What is the Point of Moral Philosophy? Edited by Roger Crisp, Ingmar Persson and Julian Savulescu, Routledge, New York & London, 2025.

The views expressed by the authors are their own and do not necessarily reflect those of UNESCO.