Remembering the Future

Or explaining what went wrong (think testing)

via Rattlesnake

1. Unknown unknowns: a five year old child does not know that he does not know calculus. For him or her, calculus is an `unknown unknown'.
2. Known unknowns: an older child know he that he does not know calculus. For him or her, calculus is a `known unknown'.
3. Unknown knowns: a high school student starts to study calculus. He or she does not yet understand calculus. For him or her, it is an `unknown known'. (You will note that the focus of the first `unknown' shifts here from lack of knowledge of the general to lack of knowledge of the specific.)
4. Known knowns: after learning calculus, it becomes a `known known': it is both known to exist and understood.
5. A part of life: after learning calculus and using every day, a person may forget how much he or she knows.