Dr. Kurtz taught philosophy for 25 years at the State University of New York at Buffalo and drew broader influence through his thousands of media appearances promoting the need for skepticism and rational thinking. He counted among his supporters the astronomer Carl Sagan, authors Isaac Asimov and Martin Gardner, and the behaviorist B.F. Skinner.
Dr. Kurtz, who wrote and edited dozens of books, oversaw a sprawling organization that included the Amherst-based Center for Inquiry, the Committee for Skeptical Inquiry (formerly the Committee for the Scientific Investigation of Claims of the Paranormal) and the publishing house Prometheus Books. He also edited the Humanist, a magazine published by the Washington-based American Humanist Association.
Dr. Kurtz once defined his vision as defending "the philosophy of skepticism especially as an antidote for public gullibility and the values of the secular and humanist outlook."
His influence and prominence grew with the spread of cultlike religious movements in the 1970s as well as the purported psychic abilities of the spoon-bending media sensation Uri Geller.
"There is always the danger that once irrationality grows, it will spill over into other areas," he told the New York Times in 1977. "There is no guarantee that a society so infected by unreason will be resistant to even the most virulent programs of dangerous ideological sects."
Dr. Kurtz was disturbed by a growing tendency of news media outlets to give what he considered uncritical coverage of psychics, fortunetellers, astrologers, and sightings of UFOs and Bigfoot.
After the release of the Steven Spielberg film "Close Encounters of the Third Kind" (1977), Dr. Kurtz braced for a new round of claims regarding abductions by aliens and cattle mutilations by supernatural forces.
Speaking to The Washington Post in 1978, he warned of "a reversion to primitive credulity in the world's most technologically advanced country."
He assailed Erich von Daniken, the author of "Chariots of the Gods" and other books that fascinated millions of readers by asserting that extraterrestrial beings left behind signs of their presence in Mayan temples, the Easter Island moai and other structural wonders.
Dr. Kurtz's Committee for the Scientific Investigation of Claims of the Paranormal filed complaints with the Federal Communications Commission and two congressional subcommittees against NBC for broadcasting "Exploring the Unknown," a 1977 program narrated by actor Burt Lancaster that used a documentary-like approach to topics such as "psychic surgery" by Filipino faith healers claiming to remove a tumor by making incisions with psychic forces.