NOUN: 1. An idea that has been demonstrated as true or is assumed to be so demonstrable.
2. Mathematics A proposition that has been or is to be proved on the basis of explicit assumptions.
ETYMOLOGY: Late Latin therma, from Greek, from therein, to look at, from theros, spectator.
FB: "I'm not necessarily claiming ID to be a theory so much as a theorem. As a theorem it works much more nicely that random chance."
I'm still lost. According to the American Heritage Dictionary On-Line (Edition of 2000), if it's a theorem, you're assuming it to be true.