John Stuart Mill (1806–73) rejected orthodox religions on moral grounds. He was a great admirer of the moral character of Christ, but he never embraced Christianity, and was critical of some Christian doctrines. When he stood for elections as a Member of Parliament, he announced his refusal to answer any questions about his religious beliefs (CW 1.274). In fact, he adopted what he regarded as an alternative religion, the Religion of Humanity, which eschews any belief in an afterlife and focuses entirely on improving the condition of human beings in this life. He believed that such a non-supernatural religion could provide a sound basis for morality. But he did not publish any detailed or systematic account of religion in his own lifetime.

In her introductory note to Mill's posthumously published Three Essays on Religion, his stepdaughter, Helen Taylor, informs us that the first two essays, “Nature” and “Utility of Religion”, were written between 1850 and 1858, while the third, “Theism”, was written between 1868 and 1870. She also mentions that Mill had intended to publish “Nature” in 1873, but the other two essays were not intended for publication at the same time. She believes that the views expressed in the three essays are “fundamentally consistent” (CW 10.371).

Mill died on 7 May 1873, and the three essays were published together under the editorship of Helen Taylor in 1874. “Theism” is the essay most sympathetic to religion. In it Mill points out that polytheism, rather than monotheism, is “more natural to the human mind”, and it requires “a considerable amount of intellectual culture” before we can reach the belief in God.