With modern science we simply don't need metaphysical assumptions, since a good scientist could be an atheist, a pantheist, a deist, or a Muslim. The bottom line, if nothing else, is that science justifies itself pragmatically. We needed some assumptions to help get science off the ground and to jettison the superstitions that held us back from discovering it. But those beliefs which we might have called assumptions in a prior era are now known as the bedrock facts of science because, if for no other reason, they produce solid results. (p. 115)
In other words, science is reliable because when we relied on it in the past it delivered the goods.
Suppose you wanted to balance your checkbook, and I handed you a calculator. You might begin without preconceptions and ask, "Is this calculator accurate?" The best way to determine if the calculator can properly add and multiply is to begin with the assumption that it is accurate and test it. Punch in some numbers that you can verify by other means (either easy calculations you can perform in your head or more complicated ones you can verify with another calculator already determined to be accurate) and test your results. If the numbers add up properly, then you are safe to conclude the calculator can be relied on.
The origin of the scientific method can be attributed to Thales of Miletus, a Greek philosopher living more than a hundred years before Socrates. Thales was the first to use naturalistic assumptions regarding the origin of the world, namely, he argued that everything was composed of water. Prior to Thales, Greeks attributed all of nature to the workings of supernatural gods and heroes. Even though Thales' speculations were incorrect, his contribution was a ground-breaking idea that paved the way for naturalism and it's inordinate success in correctly describing our world.
Moreover, the results of science are breaking down superstitions around the globe, too. So in a way, as science progresses it's tearing at the heart of religious beliefs everywhere by providing the answers that religion always promised but failed to deliver. (p. 116)