I thought we had already gone through this. If your authorities are actually experts in their field AND if their is a consensus among them (that supports your argument) AND your argument is inductive, argument from authority is valid.
Wrong. I know I've seen that claim all over the web, but it's just plain wrong. In 1970 the consensus among all professional geologists was that the continents were stationary. They didn't move with respect to one another. That theory was dead wrong. The consensus was wrong, and every "valid authority" on the subject was wrong.
Experts are not infallible, so the fact that they hold a particular position, even on a subject that are supposed to be authorities on, doesn't gaurantee that their position is true.
From Wikipedia's article on the topic:
Argument from authority (argumentum ad auctoritatem), also authoritative argument, appeal to authority, and false authority, is an inductive reasoning argument that often takes the form of a statistical syllogism.[1] Although certain classes of argument from authority can constitute strong inductive arguments, the appeal to authority is often applied fallaciously.
Fallacious examples of using the appeal include:
cases where the authority is not a subject-matter expert
cases where there is no consensus among experts in the subject matter
any appeal to authority used in the context of deductive reasoning.
I get the impression, here and elsewhere, that you don't always read everything I write.
Wikipedia is wrong, and I already quote the comments that explain why it's wrong. There is no "valid authority" when it comes to truths about nature.