As people grew accustomed to writing down their thoughts and reading the thoughts others had written down, they became less dependent on the contents of their own memory. What once had to be stored in the head could instead be stored on tablets and scrolls or between the covers of codices. People began, as the great orator had predicted, to call things to mind not “from within themselves, but by means of external marks.” The reliance on personal memory diminished further with the spread of the letterpress and the attendant expansion of publishing and literacy. Books and journals, at hand in libraries or on the shelves in private homes, became supplements to the brain’s biological storehouse. People didn’t have to memorize everything anymore. They could look it up. But that wasn’t the whole story. The proliferation of printed pages had another effect, which Socrates didn’t foresee but may well have welcomed. Books provided people with a far greater and more diverse supply of facts, opinions, ideas, and stories than had been available before, and both the method and the culture of deep reading encouraged the commitment of printed information to memory.
