All theories are subject to revision as new knowledge is discovered. That is how science advances.
Theory: a coherent group of tested general propositions, commonly regarded as correct, that can be used as principles of explanation and prediction for a class of phenomena: Einstein's theory of relativity. Synonyms: principle, law, doctrine. (from www.dictionary.com)
From the Wiki article, Scientific Theory:
Echoing the scientific philosopher Karl Popper, Stephen Hawking in A Brief History of Time states, "A theory is a good theory if it satisfies two requirements: It must accurately describe a large class of observations on the basis of a model that contains only a few arbitrary elements, and it must make definite predictions about the results of future observations." He goes on to state, "Any physical theory is always provisional, in the sense that it is only a hypothesis; you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory." The "unprovable but falsifiable" nature of theories is a necessary consequence of using inductive logic.
The defining characteristic of a scientific theory is that it makes falsifiable or testable predictions. The relevance and specificity of those predictions determine how potentially useful the theory is. A would-be theory that makes no predictions that can be observed is not a useful theory. Predictions not sufficiently specific to be tested are similarly not useful. In both cases, the term "theory" is hardly applicable.
Additionally, a theory is generally only taken seriously if:
It is tentative, correctable, and dynamic in allowing for changes as new facts are discovered, rather than asserting certainty.
By any of these measures, the Theory of Evolution is valid scientific theory. I've used it many times to make testable hypotheses.
I think I’ve said that . . . many times, but lately in #512, this thread.
“Echoing the scientific philosopher Karl Popper, Stephen Hawking . . . ”
Really?! You’ve previously informed us (in #512 and #520) that you had never heard of Karl Popper. (“Karl Popper is almost unknown among scientists. I do not recall ever hearing his name before”)
Apparently this thread has made you acquainted with the mysterious and obscure Karl Popper. Further, it would appear that even so eminent and acclaimed a modern scientist as Stephen Hawking knows of the nebulous Mr. Popper (as do most all scientists, if the truth be acknowledged).
Now you’re having a continuing discussion on Mr. Popper with a few other correspondents, so I will leave you to your discussions, following its progress with interest.
In the meantime, the observations you attribute to Mr. Hawking represent a brief summation of two thousand years’ thinking of Western Civilization Philosophy on the subject of the ‘Scientific Method’ upon which hangs the entire future of your chosen career.