We have Ohm's law, Thévenin's theorem, Pythagoras' Theorem and the law of gravity. When does a theory become a law?

 

You'll probably find that a theory and a theorem aren't the same thing.

http://en.wikipedia.org/wiki/Theorem

 

I understand the OPs point though, Theory of Electricity, Theory of Evolution.

These are hypothesis to describe observed phenomena.

A natural Law tends to be the math used to describe these theories, and are extremely consistent when used.

Even then a flawed Law can be extremely useful, such as Newton's Laws of Motion and his Law of Gravitation. General Relativity has replaced them, but interestingly when you simply General Relativity to normal conditions the math becomes Newton's Laws. For example, the math used to land a spaceship on the moon was Newton's Laws.

 

Law or theory - all subject to Murphy's Law?

 

Law or theory - all subject to Murphy's Law?

agreed!!