In an Uncertain World by Robert Rubin, Jacob Weisberg

in basic questions. His style was unadorned simplicity. Demos would walk onto the stage in the lecture hall, turn over a wastepaper basket on a desk, and use that as his lectern. He communicated a feeling of vast respect for those philosophers he regarded as great thinkers, such as Plato, Aristotle, Kant, and Spinoza. Trying to understand what these authors were saying was very challenging for me. Then, some way into our yearlong course, Professor Demos assigned the work of several authors whose thinking was not so rigorous. They were easier to understand, but we quickly became aware of the fault lines in their logic. We then went back to Aristotle and Kant with new appreciation for their intellectual power.
    Although Demos revered philosophers such as Plato who believed in provable certainty, he instilled in us the view that opinions and interpretations were always subject to revision and further development. He would turn to Plato or one of the other philosophers to demonstrate to us that proving any proposition to be true in a final or ultimate sense was impossible. Demos encouraged us not only to understand the logic of the analysis but to find the point at which the edifice rested on hypothesis, assumption, or belief.
    These ideas struck a chord with me; I even considered majoring in philosophy. Although I didn’t ultimately do that, my year with Demos spurred my developing tendencies toward skepticism and critical thinking. I often encapsulate my Demos-inspired approach by saying, “There are no provable absolutes”—a stance bolstered by the larger Harvard ethos of that period. The mind-set among my classmates was one of not accepting dogma, of questioning authority—and in retrospect, I’d say the most valuable development I took away from college was the attitude of never taking propositions at face value, of evaluating everything I heard and read with an inquiring and skeptical mind. But the seed that Demos cultivated and that Harvard nurtured didn’t lead to just skepticism. Once you’ve internalized the concept that you can’t prove anything in absolute terms, life becomes all the more about odds, choices, and trade-offs. In a world without provable truths, the only way to refine the probabilities that remain is through greater knowledge and understanding.
    Years later, when I discussed this with Alan Greenspan, he told me that the assertion “All is uncertain” is inherently contradictory because it asserts that uncertainty itself is certain. I didn’t choose to debate the matter with Alan at the time, but one answer is that he was right—the basic assertion of uncertainty is unprovable. But that just leaves us back where we started—nothing is provably certain.
    Academically, my plan at Harvard was conventional. Most people who were headed for law school, as I loosely assumed I was, majored in government. I started doing that and then switched to economics. In those days, the focus in economics was largely conceptual, and I found it difficult but engrossing; later, when the field had become much more rigorously econometric, I would not have had adequate math to major in it.
    My senior honors-thesis tutor was Thomas Schelling, the economist famous for applying game theory to international relations and thereby explaining the doctrine of nuclear deterrence. Schelling had just come to Harvard from Yale, and I was his only tutee. I spent the summer between my junior and senior years in Cambridge with no job, sleeping on a broken couch in the living room of a shared apartment, and working on my thesis to get a head start. Researching and writing in the stacks of Widener Library every day were among the few projects I really enjoyed at Harvard. My paper was about the relationship between inflation and economic development in Brazil—a subject that attracted me in part because Latin America seemed a potentially fruitful area for entrepreneurial involvement. I