"The test of a first-rate intelligence is the ability to hold two
 opposed ideas in the mind at the same time, and still retain the
 ability to function." - F. Scott Fitzgerald (The Crack-Up, 1936)

"Intelligence is the capacity to receive, decode and transmit information
 efficiently.  Stupidity is blockage of this process at any point."
 - Robert Anton Wilson

"Intelligence is like four-wheel drive.
 It only allows you to get stuck in more remote places."
 - Garrison Keillor