Wiggs,
It's an inference from the success of science, or if you like, an inference to the best explanation.
Quite: 'planes fly, pills cure etc. Try inventing anything using "faith" instead and see where that gets you, which is why nothing of value comes from theocracies. Be interesting though if one theist said to the other, "would you like a ride in this aeroplane I've designed using only the tools of faith, intuition and experience" and then seeing the reply...
The big mistake - a straw man mistake in fact - is to mis-assert that the findings of science are also claimed to be definitive or absolute, as opposed to be more probabilistically true based on the feedback we obtain from the way the world appears at least to be. That's not to say for a minute that it's necessarily not invisible pixies making it all happen behind the scenes, but it is to say that naturalistic explanations are verifiable within the context of the way the universe appears to be in a way that non-naturalistic explanations are not.
And yet the straw man response to this simple enough point recurs here time and time again.
Ah well...