When the doldrums of academe get to be too much, we occasionally challenge ourselves with brain puzzles. Here's one:
Tom Cruise ------ Nicole Kidman
A????????? ------ C???????????
B????????? ------- D???????????
\ /
\ /
\ /
Liam Neeson
Here's the challenge: standard movie game rules, and you can only use a given movie once. Actor A has to have appeared in a movie with Actor C, Actor B, and Tom Cruise. Actor B has to have been in a movie with Actor A, Actor D, and Liam Neeson. Actor C has to have been in a movie with Actor A, Actor D, and Nicole Kidman. Actor D has to have been in a movie with Actor C, Actor B, and Liam Neeson. This is indicated by the lines.
We have found the most ingenious proof, but haven't room for it here. Godspeed.