Thomas Jefferson once encountered a jaw-dropping claim.
The claim that confronted Jefferson was from eyewitnesses who said that they had seen rocks fall from the sky. They even claimed to retrieve fragments from them.
And here’s the kicker: the witnesses, under normal circumstances, would be considered pretty darn good ones: two Harvard professors.
But Jefferson did not believe their claims. Insofar as Jefferson knew, rocks don’t fall from the sky, and so the witnesses, in his estimation, were either lying or simply mistaken.
Concerning the incident, he said the following: “I could more easily believe that two Yankee professors would lie than that stones would fall down from heaven.”
Jefferson, in other words, possessed a Weltanschauung—a worldview, a paradigm, a model for the way the world is and works—that could not accommodate such a claim at face value. What Jefferson thought he already knew simply did not match what the witnesses said. He saw no way to make the claim and his existing model cohere, and so he dismissed it and did not question his model. He concluded that it was physically impossible for such a thing to literally occur. We now know, of course, that rocks can and do sometimes fall from the sky—as meteors.
In this instance, Thomas Jefferson’s error was the following: he did not bring critical reflection upon both the new claim and his existing view of the world. It was good that he sought coherence between the claim and his worldview (coherence is crucial to critical thinking: what we think we already know about the world should match new claims about the world). But Jefferson failed to reevaluate what he took for knowledge in the light of a new and emphatic claim from otherwise reliable sources: two Harvard professors.
There are three lessons here: (1) worldviews—your own and others—should be made explicit in the evaluation of claims, for they profoundly color interpretations of evidence; (2) when confronting a new claim, bring as much critical skepticism to what you think you already know as you do to the new claim; and (3) seek coherence: new claims should fit into a larger framework of knowledge.
For critical thinking tip #3, see here.