[mannykannot]

you have a point - they are not exact analogies - but, as you say, we came up with those ideas after we had an understanding of the system. If we can discover things without having a prior definition of them, then having a vague prior definition should be no obstacle - even if it leads to some initial confusion, clearing that up through the gathering of evidence should be no harder than coming up with a definition for something we previously did not suspect through the gathering of evidence.

This is so even if it turns out that the phenomenon does not exist, such as in the case of the mythical causal effects of the four humors.