Paul Kurtz, a philosopher whose advocacy of reason ahead of faith helped define contemporary secular humanism, died on Saturday at his home in Amherst, N.Y. He was 86.

He had been treated for chronic obstructive pulmonary disease, said his son, Jonathan, who is the president of Prometheus Books, the publishing house his father founded in 1969, and who confirmed the death.

Professor Kurtz taught philosophy at the University at Buffalo, part of the State University of New York, from 1965 until his retirement as professor emeritus in 1991. But his wider influence came as a publisher of books and magazines devoted to fact-based, rather than faith-based, solutions to human problems, and as a writer who, in more than 40 books and hundreds of articles, promoted an ethical system independent of religion.

Professor Kurtz founded the Center for Inquiry, which promotes evidence-based reasoning and opposes organized religion, and the Committee for the Scientific Investigation of Claims of the Paranormal (known as Csicop), which is dedicated to debunking pseudosciences.