"Moreover, it cannot be true that the sole purpose of a scientific theory is to predict the results of experiments. Why on earth would anyone want to predict the results of experiments? Most of them have no practical use; and even if they had, practical usefulness has nothing to do with scientific inquiry. Predicting the results of experiments is not the purpose of a theory, it is a test to see if the theory is true. The purpose of a theory is to understand the physical world"The book is out of print, but you can download the full text here, and the above quote is on p.214.
In contrast, R.P. Feynman's textbook said:
Another thing that people have emphasized since quantum mechanics was developed is the idea that we should not speak about those things which we cannot measure. (Actually relativity theory also said this.)In relativity, someone could ask: What is the real time? Are the events really simultaneous? Do the rods really contract or just appear to contract? Why do the twins age differently?
At some point, you have to accept the fact that if you ask questions that cannot be resolved by experiment, then you may not get a satisfactory answer. You may not get that understanding of the physical world that you desire.
One of the main points to XX century physics is to stick to what is measurable. Sudbury wants more out of a scientific theory. I take the more positivist view. Speculate about unobservables all you want, but face the fact that if there is no experiment to say whether you are right or wrong, then you have left the domain of science.