Is There an Ultimate Theory?
There is a very interesting paper circulating online, originally submitted to the annual FQXI essay contest by Dr. Strophren, related to whether or not there can ever be a theory of everything. According to the simple but elegant proof put forth in this article, there can be no final scientific theory that explains everything.
The argument the author uses is that the number of possible states of the Universe is uncountable. (This is actually easy to prove, since any space-time in any dimension actually contains an uncountable number of 'points' in space and time, so to describe every point at every time is also uncountable). It also uses a proof similar to Godel's proof in mathematics that there only exists a countable number of theories or laws of physics.
Obviously if you can count the possible theories and not the possible states of the Universe, then almost every state of the Universe is undescribable by a theory - or another viewpoint is that every theory describes an infinite number of possible Universes and so it follows that a deeper theory is need to separate the possibilities.
It is quite a beautiful proof, even if it is bordering on philosophy, and one that isn't too hard to follow for the layman.