That is a characature, but it is close enough to a definition of science: The search for natural explanations, as opposed to the acceptance of supernatural explanations.
Without such an assumption, we would still be explaining volcanos and earthquakes as the rumblings of an angry god or gods. Same for storms and disease and the movements of the planets.
Only problem w/ this approach is that if you *are* looking at a supernaturally-created cosmos and biology, limiting your potential explanations to purely natural ones will *guarantee* that you will get the *wrong* answer.
Since the foundational question is whether we are looking at a natural vs supernatural creation, to limit acceptable explanations to only natural ones means that natural explanations are correct 'by definition' only.
Don't know if you can understand that or not.