[pdonis]

> no mechanism for head pain reliev is known, but we know that some medication works

Yes; I would not consider this as evidence in favor of any scientific model, since, as you note, we don't have a scientific model that predicts what drugs should relieve headache pain. It's just an empirical generalization; as an empirical generalization, yes, it has a solid track record of accuracy behind it, but only as an empirical generalization, not as support for any scientific model. Of course we humans have lots of empirical generalizations we use all the time that are similarly not based on any scientific model. I am certainly not claiming that we should not make use of such generalizations when we have them. We just shouldn't confuse them with scientific models.