Before beginning any research, first ask, “Does anything about the assertion seem suspicious or unlikely on its face?” For example, early in The Vinci Code, Brown claims that over a period of three hu

Before beginning any research, first ask, “Does anything about
the assertion seem suspicious or unlikely on its face?” For example,
early in The Vinci Code, Brown claims that over a period of three
hundred years, the Catholic Church burned five million witches at
the stake in Europe around the fifteenth was immediately
suspicious of this “fact,” so took out my calculator and did the math.
Rome would have to burn forty-five women a day, every single day,
nonstop for three hundred years. a lot of firewood.
Furthermore, a quick internet search revealed that the popula-
tion of Europe at the time was about 50 million. If half were female
(25 million) and half of those were adults (12.5 million), then some-
thing like 40 percent of the entire adult female population perished
at the hand of the Vatican. That’s more carnage than the Black Plague
of 1347, which killed only one-third. Let’s just say this seems highly
unlikely.