re: Scientific Laws = Articles of Scientific Faith
Er, no, they don't assume them to be true. They (the scientists) come up with testable hypothesis about the data that's been gathered. If the preponderance of evidence supports the hypothesis then the hypothesis may become a theory. Like the theory of gravity for instance. If there isn't sufficient evidence then it remains a hypothesis. And here's the important part; if new evidence comes to light then the theory is either modified or discarded.
And when it comes to gravity. There is a theory of gravity: how we *think* it works, and there is the fact of gravity: we are held on to the earth.
Finally, in science there is no proof. Just evidence that fits theories. Science tries to explain what happens in nature/universe; it doesn't prove anything. Of course some theories have a *lot* of evidence. The TOE has much more evidence, say, than the various theories of gravity.