Peter Singer
1946 CE – Present · Contemporary Era
“If it is in our power to prevent suffering without sacrificing anything of comparable moral importance, we ought to do it.”
Biography
The world's most influential living ethicist. Singer's Animal Liberation launched the modern animal rights movement by arguing that the capacity to suffer, not species membership, is what matters morally. His work on global poverty argues that affluent people are morally obligated to give substantially more to those in extreme need. He is the intellectual architect of the effective altruism movement.
Major Works
Key Arguments
Click “Philosophy 101” to read the full exploration of each argument.
The Expanding Circle and Animal Liberation
Singer argued that the moral circle has expanded throughout history, from tribe to nation to humanity, and that logical consistency demands one further expansion: to all sentient beings capable of suffering. Discriminating against animals merely because they belong to a different species is 'speciesism,' morally analogous to racism or sexism. What matters morally is not intelligence, language, or rationality but the capacity to suffer. A being that can feel pain has an interest in not suffering, and that interest deserves equal consideration regardless of species. Factory farming, which inflicts massive suffering on billions of sentient creatures for trivial human preferences, is therefore one of the great moral catastrophes of our time.
Why it matters: Animal Liberation (1975) launched the modern animal rights movement and gave it its philosophical vocabulary. Singer's argument did not require attributing 'rights' to animals (he is a utilitarian, not a rights theorist), only that their suffering be counted. The book directly inspired changes in law, farming practices, and consumer behavior worldwide, and made 'speciesism' a standard term in ethical discourse.
Famine, Affluence, and Morality
If you walked past a shallow pond and saw a child drowning, you would wade in to save the child, even if it meant ruining your expensive clothes. The cost to you would be trivial compared to the life saved. Singer argued that the same logic applies to global poverty: people in affluent countries can prevent suffering and death by donating to effective aid organizations, at a cost that is trivial compared to the lives saved. Geographic distance and the number of other people who could help are morally irrelevant. If we can prevent something bad from happening without sacrificing anything of comparable moral importance, we ought to do it. This means the ordinary spending habits of affluent people, dining out, buying new clothes, upgrading technology, are morally indefensible while children die from preventable diseases.
Why it matters: A widely discussed paper in contemporary ethics. First published in 1972, the 'drowning child' argument has never been convincingly refuted on its own terms, though many philosophers have tried. It provided the intellectual foundation for the effective altruism movement, which channels billions of dollars toward the most cost-effective charitable interventions.
Preference Utilitarianism and Practical Ethics
Singer refined classical utilitarianism by arguing that what matters is not maximizing pleasure but satisfying preferences, giving beings what they actually want, not what we think would make them happy. This framework allowed him to address controversial issues with unusual directness. He argued that severely disabled newborns in some cases may be ethically euthanized (since they lack preferences about their future), that there is no intrinsic moral difference between killing and letting die, and that our obligations to future generations depend on whether they will exist to have preferences. These positions provoked fierce controversy, but Singer maintained that moral philosophy must follow arguments wherever they lead, even to uncomfortable conclusions.
Why it matters: Singer demonstrated that applied ethics could be rigorous, consequential, and deeply uncomfortable. His willingness to follow utilitarian logic to its conclusions, including conclusions that most people find repugnant, forced the philosophical profession to take applied ethics seriously and to confront the gap between moral theory and moral intuition. Practical Ethics (1979) remains a standard textbook in the field.
Lasting Influence
Launched the animal rights movement and effective altruism. The most widely read living philosopher. His arguments on animal suffering are more defensible than his arguments on infanticide, which reveal what happens when a utilitarian framework defines moral status in a way that guarantees its preferred conclusions.
Your Reading Path
The Companion Guide
Seven eras of philosophy in one volume — reading lists, key terms, journal prompts · $19.99