Before he became the third president of the United States, Thomas Jefferson sat down to compose the Declaration of Independence. “We hold these truths to be self-evident, that all men are created equal,” he wrote. At the time, he was a slave-owner. Hypocrisy aside, there’s a “duh” factor in saying “all men are created equal,” but Jefferson must have found value in the proclamation of a self-evident truth. The fact that he needed to spell it out might have reflected the reality that we didn’t then live in a world where all men were treated equally—and we don’t now.