What are its relations to metaphysical explanation?
Physicists, philosophers, theologians, and any scholar who strives to be humble before the Ultimate Truth of the Real: attend.
Have you ever stopped to consider these questions? Reserve some time for yourself to read the following excerpt, then be silent and do some real work on this matter. It will repay you with a renewed energy and enthusiasm as you go back to your daily tasks.
What is the value of physical theory? What are its relations to metaphysical explanation? These are lively questions today, but like so many central questions, they are by no means new. They belong to all time: they have been raised as long as a science of nature has been in existence. The form in which they are cloaked may change somewhat from one century to another; the form of the questions derives from the science of the day and is variable; but one need only remove this covering to become aware that essentially the questions remain the same.
Until we reach the seventeenth century, we come upon very few areas of natural science that have advanced to the point of formulating theories in mathematical language, theories whose predictions are expressed in numerical terms so that they can be verified by comparison with the measurements furnished by precise, direct observation. Even statics, then called scientia de ponderibus, and "catoptrics," at that time subsumed under "perspective" (our "oprics"), had barely reached this stage of development. Bypassing these two limited areas, we encounter only one science with a form which, even at that time quite advanced, would cause us to anticipate the course taken by our modern theories of mathematical physics: that science is astronomy. Hence, where we today speak of "physical theory," the Greek or Arabic philosophers and the medieval or Renaissance scientists spoke rather of "astronomy."
No other area of natural science had yet reached that srate of perfection where the language of mathematics serves to express laws discovered by exact observation. Physics in our sense, as both mathematical and empirical, had not yet become separated from the metaphysical study of the material world, that is, from cosmology. In many instances, therefore, where we would today speak of "metaphysics," the ancients used the word "physics" instead.
This is why the question so much discussed today - What are the relations between physical theory and metaphysics? - was for the two thousand years formulated differently - What are the relations between astronomy and physics?
[Duhem, To Save the Phenomena: an essay on the idea of physical theory from Plato to Galileo, introduction. Translated from the French by Edmund Doland and Chaninah Maschler, with an introductory essay by S. L. Jaki (Chicago and London: The University of Chicago Press, 1969)]