I believe it would be entirely possible to have two opposing, mutually exclusive theories, both of which match all the known observables.
Maybe that's where faith starts...
Here's the exact problem. The theory is the "observables". If two theories predict the same result, then they are the same theory. Since the "explanation" part is not subject to scienctific verification, it is not part of the pure science. Explanations are often tacked on because it can be difficult to describe scientific results as pure observations, and it is not uncommon for these tacked-on explanations to be included in the actual theory by casual readers, unfortunately.