One way is to ask a selection of people representative of the population if they believe in ghosts.
Another is to ask what they fear.
Such beliefs have pervaded American culture and media for centuries.
Last year, the share of Americans who belong to religious congregations fell below 50 percent for the first time in more than 80 years, according to a Gallup poll released in March.
Paranormal television, film and media of all sorts also play a significant role in the perpetuation of belief in the supernatural.
“Ghost Hunters,” which premiered in 2004 and originally ran for 11 seasons, portrayed the search for paranormal activity as a discipline.
The site added a new element to these stories by making them interactive, with readers going back and forth in the comments, joining and adding to the narrative themselves.
Mr. Baker, the co-author of “American Secularism,” put it another way.
“There was certainly a real spike in people who sought the services of mediums, sought comfort in spiritualism about the time of the American Civil War,” she said.
Then as now, the paranormal was fodder for connection.
Today, believing in some form of the paranormal may represent freedom in another way, perhaps as an avenue to conceptualize other possibilities.