In retrospect, professors who must have disagreed fundamentally with works such as David Donald's "Lincoln Reconsidered" (with its celebrated explanation of the abolitionists' contempt for Lincoln in terms of the loss of status of their fathers' once-privileged social group) assigned them for our open-minded academic consideration. My professor of Tudor-Stuart history, emerging from the bitter Oxbridge debates over explanations of the English Civil War in terms of class conflict, assigned Jack Hexter's stunning "Reappraisals in Social History" to us. When I opined to him somewhat apprehensively that Hexter appeared to have exposed the tendentious use of statistics in my professor's own prior work, he replied, "You're absolutely correct." These were not uncommon experiences in Princeton's classrooms, and I knew, then and there, that I wanted both to do history and to teach.

In grad school at Harvard, while a few dates left in the midst of dinner on discovering my free-market and hawkish politics, and while I did get thrown out of a party for opposing, when asked, Eugene McCarthy's view of Vietnam (this should have been a warning), the classroom remained open and, by design, intellectually pluralistic. In our graduate colloquium, we read the major historiographical debates, in works theoretical and monographic, and critical acumen was acknowledged in the force of an argument, not in its political provenance. When Harvard exploded, in 1966–67, I was in Paris, researching my dissertation in the Bibliothèque Nationale; when Paris blew up the next year, I was locked away in Cambridge, Mass., finishing my dissertation. (My friends on the left, only partly in jest, explain my backwardness by my having missed two revolutions.) When I went off on job interviews, I was not once asked a question, ever, about my worldview, but only about my historical research and notions of teaching. Politics were simply not in the category of appropriate inquiry.

In social contexts, up through the 1970s, some few colleagues might be harsh over our political differences, but most loved the idea of individuals who thought differently from themselves. In the midst of the "cultural revolution" of the early 1970s, I co-founded a College House and lived warmly with students who mostly ranged from liberal Democrats to true believers of the New Left. They loved to discuss everything, and they did so in good faith and (almost) always ad rem. My students, whom I still meet frequently outside of class, still love to discuss everything, and they still do so in good faith and without ad hominem distractions from real conversation and debate. Critics of higher education who blame students for today's catastrophes are categorically wrong about agency. It is the faculties (both the minority of zealots and the majority of cowards) and the administrations (both the minority of ideologues and the majority of careerists with double standards) who are to blame.

The academic world I so loved revealed itself best in an undergraduate course I'd taken on the history of Europe in the 20th century. When the professor, a distinguished intellectual of the left, returned the midterms to the hundred-plus or so of us who were in his course, he said that we'd saddened and embarrassed him. "I gave you readings that allowed you to reach such diverse conclusions," he explained, "but you all told me what you thought I wanted to hear." He informed us that he would add a major section to the final exam: "I'm going to assign the book I disagree with most about the 20th century. I'm not going to ask you to criticize it, but, instead, to re-create its arguments with intellectual empathy, demonstrating that you understand the perspectives from which he understands and analyzes the world." I was moved by that. The work was Friedrich Hayek's "The Road to Serfdom," and it changed the course of my intellectual and moral life.