Can a person’s greatness be recognized only in retrospect, by those who live after the person, as the speaker maintains? In my view the speaker unfairly generalizes. In some areas, especially the arts, greatness is often recognizable in its nascent stages. However, in other areas, particularly the physical sciences, greatness must be tested over time before it can be confirmed. In still other areas, such as business, the incubation period for greatness varies from case to case. We do not require a rear-view mirror to recognize artistic greatness, whether in music, visual arts, or literature. The reason for this is simple: art can be judged at face value. There’s nothing to be later proved or disproved, affirmed or discredited, or even improved upon or refined by further knowledge or newer technology. History is replete with examples of artistic greatness immediately recognized, then later confirmed. Through his patronage, the Pope recognized Michelangelo’s artistic greatness, while the monarchs of Europe immediately recognized Mozart’s greatness by granting him their most generous commissions. Mark Twain became a best-selling author and household name even during his lifetime. And the leaders of the modernist school of architecture marveled even as Frank Lloyd Wright was elevating their notions about architecture to new aesthetic heights. By contrast, in the sciences it is difficult to identify greatness without the benefit of historical perspective. Any scientific theory might be disproved tomorrow, thereby demoting the theorist’s contribution to the status of historical footnote. Or the theory might withstand centuries of rigorous scientific scrutiny. In any event, a theory may or may not serve as a springboard for later advances in theoretical science. A current example involves the ultimate significance of two opposing theories of physics: wave theory and quantum theory. Some theorists now claim that a new so-called “string theory” reconciles the two opposing theories-at least mathematically. Yet “strings” have yet to be confirmed empirically. Only time will tell whether the string theory indeed provides the unifying laws that all matter in the universe obeys. In short, the significance of contributions made by theoretical scientists cannot be judged by their contemporaries, only by scientists who follow them.