Thirst

"School [high school] provides drinking water--but it doesn't create thirst."
Tim Clydesdale in The First Year Out

Fish

"Whoever first discovered water, we know it wasn't a fish."
John Maxstadt in the ili-l listserv

Fundamental of Critical Thinking

"The first goal of a rational thinker is that, once a theory is formed, evidence that conflicts with this theory is sought. Searching to be proven wrong, rather than vindicated, is a cornerstone of critical thinking."
from http://howto.lifehack.org/wiki/Critical_Thinking