Epistemology

Roman concrete was not lost. Roman concrete remains, embedded in the Pantheon’s dome and in thousands of bridges and aqueducts that have stood for two thousand years. Vitruvius wrote down the recipe in the first century BCE. The texts have been continuously available. The materials still exist. By any reasonable test, the information about Roman concrete has been with us the entire time. What was lost, for roughly 1,400 years, was the ability to make it....

Aristotle wrote about eels in Historia Animalium around 350 BCE. He observed that they had no testes, no ovaries, no obvious reproductive organs of any kind. He concluded — reasonably, given what he could see — that eels must arise spontaneously from mud. Specifically, from the entrails of the earth. This was wrong. Twenty-three hundred years later, we know it’s wrong. We also still cannot reliably explain, in much detail, how eels reproduce....