"Science" Defined

What, if anything, can "science" tell us about value, or about God's existence or non-existence? To get at these things it seems obvious that we need some shared idea of just what "science" is. How shall we define "science?" Alvin Plantinga, in his Stanford Encyclopedia of Philosophy entry "Religion and Science," shows just how difficult it is to give "science" any definition. What shakes down for him, after explaining various ideas about science, is this:

"Perhaps the best we can do, with respect to characterizing science, is to say that the term ‘science’ applies to any activity that is (1) a systematic and disciplined enterprise aimed at finding out truth about our world,[1] and (2) has significant empirical involvement. This is of course vague (How systematic? How disciplined? How much empirical involvement?) and perhaps unduly permissive. (Does astrology count as science, even if only bad science?) Still, we do have many excellent examples of science, and excellent examples of non-science."

If we have examples of science and non-science why, then, is it important to define "science?" And if we have trouble doing this, so what, since we have excellent examples of both science and non-science? Because, among other things, of the need to be able to judge the many claims that do not have essentially to do with the doing of science, but rather concern "science" as such. As, for example, the statement Science and religion conflict.