Born in Brooklyn, New York, in 1934, Sagan followed his inquisitive mind and aptitude for learning to a PhD in astronomy and astrophysics and positions teaching at Harvard, and later Cornell, where he was an astronomy professor for 30 years. He was a special consultant to NASA and the American Air Force in the 1950s, later contributed to SETI, and was instrumental in bringing basic astronomical education to the masses through his wildly successful public broadcasting show Cosmos: A Personal Journey. Sagan's work as a popularizer of science and subsequent celebrity allowed him to promote skeptical inquiry to a wide audience. He became known for his advocacy of the practice, writing several well-received articles for popular publication, some of which comprise his initial work on The Demon-Haunted World.

Sagan uses himself as a case study throughout The Demon-Haunted World, aligning his biographical information with discussions of learning, such as going to museum with his parents or reading baseball statistics with his father. This is the main point of the work—that the quest for knowledge is one of progression, not stasis. Sagan uses his biography to promote the humanity of scientists, who cannot ever be completely free of their own biases.