[RogueIsland]

I always thought that theories were advanced to explain observed phonomena, not for prediction.

Actually, theories must be predictive as well as explanatory.

[Frumious Bandersnatch]

I know this may be splitting hairs, but I believe that a theory can be used in making predictions, but the theory itself only describes a set of observed phenomona. For example the General Theory of Relativity describes the relationship between energy and mass. It does not predict anything. Using the theory, however, we are able to predict the ability to build an atom bomb.