The most important lesson this fall, common to all classrooms, is an appreciation for evidence. All disciplines have standards of evidence. The power of liberal education lies, in part, in the diversity of these standards, in the different ways disciplines require that an argument be woven, substantiated, and articulated.

Consider the simple question that can be posed from kindergarten to a PhD dissertation defense: “How do you know that?” From the earliest age, a child can learn that assertion is not enough. “Because I say so,” offers no reason to raise one narrative, argument, or claim above another. “I read it on the internet” isn’t much better. Education is a process by which a student learns how to find, sift, and organize evidence while at the same time gaining the critical thinking skills necessary to evaluate evidence and identify claims based on mere assertion. All students should also learn that “How do you know that?” is a legitimate question, rather than an existential challenge.

Eventually students should acquire an understanding of context: in this case, the difference between the nature of evidence in a laboratory, a courtroom, a debate forum, or a legislative hearing. These spaces map roughly onto disciplines – sciences, law, rhetoric, political science. Other disciplines take their evidence from texts, or from works of art and music. Students at all levels can learn to use these different forms of evidence to build stories about past and present, near and far. And in each case, an instructor can ask them “how do you know that?”

As a historian, I look for evidence from the past, an activity (and then a skill) accessible to students from an early age given the cornucopia of available digitized visual sources. Our evidence, like our rules for using it, differs from colleagues in other disciplines. Unlike a scientist we cannot create evidence, other than perhaps oral histories. Nor can we replicate data, and hence must learn to balance intellectual confidence with uncertainty. We invoke – carefully and critically – evidence that would be dismissed as “hearsay” in a court of law. We look for the most compelling narrative, a tapestry of disparate sources that can be quantitative, visual, material, written, or oral; ours is a standard more attainable than a courtroom’s requirement of “beyond a reasonable doubt.”

These different forms, protocols, and standards of evidence enable students eventually to choose which modes they find most interesting. Careers are built on such choices. But so are communities and civic cultures. The voter needs to respect evidence every bit as much as the civil engineer and the physician. That respect begins in the classroom.