Also: Don't get so enamoured by the idea of incremental progress, of scientific legacy, that you can scarcely imagine the idea that everybody you know might have taken a wrong turn 30, or 50, or 400 years ago. Science is the study of what is _not_ true, of falsification: how _not_ to cure a patient, how _not_ to go to the moon. It says nothing about what _is_. (That's the domain of engineering.)

The discovery of germs did not prove the non-existence of prions.