Predicting Correctly Every Time

Doctor Kildursnt used to take a sage green-notebook in his kit when visiting expectant mothers. In the course of the visit about half of the time he would say, "The baby you are carrying is a boy." and make a note in the sage-green notebook. Later when Mrs. Jones' baby boy was born he would say, "...just as I told you." In the case that Mrs. Jones' baby was a girl he would say, "Let me look in my book." Then he would point out that in the sage-green notebook he had written: "Mrs. Jones, baby girl" along with the date of the visit in a long column of entries.

At Lunarpedia there is some use of the same principle. The List of Propulsion Systems article contains some mutually exclusive entries. If the list contains every concept any contributor can imagine, there is some chance that moon launched propulsion system actually used will be one predicted in Lunarpedia.