In the 1950s, students in America were taught that Thomas Jefferson was a great man because he wrote in the Declaration of Independence that “all men are created equal.”
Then in the 1960s, African-Americans fought for equal rights, there was a feminist movement, and an intellectual/academic movement known as post-modernism emerged.
Historians responded by looking for African-Americans and women in the American past, and by questioning written sources, rather than simply accepting as “truth” what was written in the past.
Today students in America are taught that Thomas Jefferson wrote in the Declaration of Independence that “all men are created equal,” but they are also taught that Jefferson owned slaves from Africa, and that women were not allowed to vote in America at that time. In other words, students are now taught to not accept what was written in the past as “the truth,” but instead are encouraged to understand the past in all of its complexity.