Nostradamus was a 16th-century seer. He and his prophecies—revered by some, ridiculed by others—are still well known today, centuries after he lived, and continue to be the subject of debate.

Nostradamus was born in France in 1503. He first worked as a physician and began his medical practice in the 1530s, although he did so without a medical degree. He began making prophecies about 1547, and he published his prophecies in a book entitled Centuries (1555). He wrote his prophecies in quatrains: four lines of rhyming verse. The quatrains were grouped in hundreds; each set of 100 quatrains was called a century. Nostradamus gained notoriety during his lifetime when some of his predictions appeared to have come true. He was highly sought after and was even invited to the court of Catherine de’ Medici, then the queen consort of King Henry II of France, to create horoscopes for her children.

Nostradamus’s predictions tended to be about general types of events, like natural disasters and conflict-related events that tend to occur regularly as time goes on. Some people believe that his prophecies have predicted actual events, such as the death of Henry II, the French Revolution, the rise of Napoleon, the rise of Adolf Hitler, and the 9/11 attacks. Others maintain that because his prophecies tend to be about general types of events that occur frequently throughout history—and are written in a cryptic and vague manner—it’s possible to find one that seems to match almost any event that has occurred.