I came across a webpage which makes this claim."Skeptics of homeopathy insist that homeopathic medicines do not work, but have difficulty explaining how so many people use and rely upon this system of medicine to treat themselves for so many acute and chronic diseases." Is there a name for the kind of fallacy this person is making or particular way to describe it? I feel like that even if I couldn't explain why so many people "rely" on Homeopathy that doesn't mean that it is a valid form of medicine.

You are probably thinking of the informal fallacy, Argument ad Populum or Appeal to the Masses, in which someone suggests a conclusion is true because many people believe it to be true. http://en.wikipedia.org/wiki/Argumentum_ad_populum While large-scale belief might provide inductive evidence for some claims, we know the masses can be wrong about lots of things, especially in cases where the underlying explanations are complex, as in medicine. That most people believed the sun goes around the earth did not show that claim is true. That most people did not (do not?) believe tiny things (germs) cause disease does not show that belief is true. That many people think homeopathy works provides little or no support for that claim. However, there's an interesting twist in this case: the placebo effect is remarkably powerful--if people believe some medical treatment works, that belief can have effects, especially when it comes to pain. So, many people believing homeopathic treatments work might...