When Simonides and Peter of Ravenna were alive, books and pens were not widely available for people to write notes with, so people had to remember what they learned.
Mary Carruthers is the author of The Book of Memory, a study of the role of memory techniques past.
She writes, "Ancient and medieval people reserved their awe for memory."
In other words, these people thought that a genius was a person with excellent memory.
They considered memory to be a art and a great virtue because a person with a good memory could turn external knowledge into internal knowledge.