Isaac Saul in Persuasion:
Many of the things that you believe right now—in this very moment—are utterly wrong.
I can’t tell you precisely what those things are, of course, but I can say with near certainty that this statement is true. To understand this uncomfortable reality, all you need is some basic knowledge of history.
At various times throughout the history of humankind, our most brilliant scientists and philosophers believed many things most eight-year-olds now know to be false: the earth was flat, the sun revolved around the earth, smoking cigarettes was good for digestion, humans were not related to apes, the planet was 75,000 years old, or left-handed people were unclean.
Around 100 years ago, doctors still thought bloodletting (that is, using leeches or a lancet to address infections) was useful in curing a patient. Women were still fighting for the right to vote, deemed too emotional and uneducated to participate in democracy, while people with darker skin were widely considered subhuman. The idea that the universe was bigger than the Milky Way was unfathomable, and the fact the earth had tectonic plates that moved beneath our feet was yet to be discovered.
More here.