Rachels's best-known work is
The Elements of Moral Philosophy. It went to its sixth edition in 2009, having been revised by Rachels's son, Stuart Rachels. Among the subjects covered are ethical and simple subjectivism, emotivism, as well as ethical and psychological egoism, to name but a few. The text uses real-world examples to highlight points regarding complicated philosophical principles. Rachels had a history of using such examples. The publication in 1971 of his anthology
Moral Problems marked a shift from teaching meta-ethics in American colleges to teaching concrete practical issues.
Moral Problems sold 100,000 copies over three editions.
In 1975, Rachels wrote "Active and Passive Euthanasia", which originally appeared in the
New England Journal of Medicine and argued that the distinction so important in the law between killing and letting die has no rational basis. Rachels claims that, if we allow passive euthanasia, we should also allow active euthanasia. He supports this claim with two more:
- Active euthanasia is more humane than passive euthanasia; and
- killing versus letting die makes no moral difference in itself.
"The End of Life" (1986), a moral treatise on life and death, broadened and deepened these ideas.
Rachels wrote only a few works that were not directly focussed on ethics.
Created from Animals (1990) made the case that a Darwinian world-view has widespread philosophical implications, including drastic implications for our treatment of nonhuman entities.
Can Ethics Provide Answers? (1997) was Rachels's first collection of papers. His second,
The Legacy of Socrates, was published posthumously in 2007. Shortly before his death, he wrote
Problems from Philosophy, an introduction to philosophy. This book was published posthumously in 2005 and revised by his son Stuart in 2008.