Arguments that fail to convince me (#1 in a very occasional series)

"The vast majority of scholars believe this, so it must be true."

That might be a good reason to believe something, it may even give me enough reason to seriously consider it and be humble about my own intellect. However, this phrase is often trotted out as though, in and of itself, it should be enough to convince me.

The vast majority of scholars have been wrong before. I'm more interested in WHY the vast majority believes something, rather than the mere fact of their belief (also, when this is used on me, I often find out that the majority isn't so vast after all).

[Note: this post is NOT about global warming. I suppose it might apply, but I'm thinking more about scholars of history, literature, and religion].