During a college engineering course, my professor proposed a question to the students. “You construct a flawless theory—airtight reasoning, clean premises, a clear and necessary conclusion. You test it through modeling. You gather data. The results don’t match the prediction. What is wrong: the theory, or the model?” The class was still for a moment, each student absorbing the professor’s questions. Half of my classmates were graduate students in the department of economics.
