from memory

Based entirely on one's memory, without having to consult some reference or be told by someone else. He has this uncanny ability to play any song from memory after hearing it just once. A: "Wow, this picture Samantha drew is incredible!" B: "I know. She did the whole thing from memory—she didn't look at a picture or anything!" How am I supposed to know the capital of Vermont from memory? You know we learned state capitals in grade school, right?