In Chapter 1, we considered the scientific method and how it guides the work of geologists. In the context of the scientific method, plate tectonics is a confirmed theory whose strength lies in its simplicity, its generality, and its consistency with many types of observations. Theories can always be overturned or modified. As we have seen, competing hypotheses about how mantle convection drives plate tectonics have been advanced. But the theory of plate tectonics itself—like the theories of Earth’s age, the evolution of life, and genetics—explains so much so well, and has survived so many efforts to prove it false, that geologists treat it as fact.
The question remains, why wasn’t plate tectonics discovered earlier? Why did it take the scientific establishment so long to move from skepticism about continental drift to acceptance of plate tectonics? Scientists approach their subjects differently. Scientists with particularly inquiring, uninhibited, and synthesizing minds are often the first to perceive great truths. Although their perceptions frequently turn out to be false (think of the mistakes Wegener made in proposing continental drift), these visionary people are often the first to see the great generalizations of science. Deservedly, they are the ones history remembers.
Most scientists, however, proceed more cautiously and wait out the slow process of gathering supporting evidence. Continental drift and seafloor spreading were slow to be accepted largely because these audacious ideas came far ahead of any firm evidence. Scientists had to explore the oceans, develop new instruments, and drill the seafloor before the majority could be convinced. Today, many scientists are still waiting for more evidence of how the mantle convection system really works.