Evolution: Principle Or Theory?

In the article "To Effectively Discuss Evolution, First Define 'Theory'" in the May 12 issue of The Scientist (R. Lewis, page 13), it was stated that the term "theory of evolution" should be replaced by "principle of evolution." Is this suggestion justified?

A theory is a plausible hypothesis that is supported by a considerable amount of evidence, while a principle is a scientific law that has been proved beyond reasonable doubt. Is evolution law or theory? To determine this, one must define evolution. If by "evolution" one means the observed genetic diversification and adaptation of species within a genus, this is a known fact. This would be in the category of principle or law. However, if by evolution one means the belief that all life evolved from a common ancestor, this would be, at best, a theory.

There is some evidence that can be used to support this...