But for most religious people, angels are far from imaginary. They are not merely cultural conceptions, symbols or myths.
Indeed, angels play a vital role in the relationship between humans and the divine, according to teachings of the world's dominant religions.
Judaism, Christianity and Islam all believe in angels and share a common notion -- that angels do God's work, including communication with humans. The very word "angel" is from the Greek translation of the Hebrew word for messenger, "mal'ach."
Many in the New Age movement embrace angels, while Buddhists and Hindus do not, although they believe in a cosmos filled with otherworldly creatures.
Almost every society in history has had stories or scriptures that deal with beings like angels, says Peter Kreeft, a philosophy professor at Boston College who has written extensively about Catholic beliefs, including a book on angels and demons.
"It seems," Kreeft says, "like the human race innately knows there is something like angels."
While various traditions agree that angels do not have wings -- those sprouted from Old Testament stories and medieval artists' depictions of mobility -- beliefs about what angels are and what angels do vary from faith to faith.