When is it rational to believe somebody's testimony?

I have argued that it is rational to accept the principle of credulity. This is the principle that, all things being equal, it is rational to accept the testimony of others.

AnAtheist.Net would agree with this in some circumstances but not others:

"let's use your example of the stranger giving directions. If said stranger tells me to go down the street, turn right, and head 3 blocks then it seems like said person knows what he is talking about. However, if the same stranger said instead that I should go into his house and use a secret tunnel that exists at my destination then I no longer have good reason to accept his trustworthiness."

So what is going on here? AnAtheist.Net explains: "The more implausible the claim sounds when measured against our background experience the more likely we are to be skeptical."

Although this statement introduces a nagging doubt, I am still largely sympathetic with AnAtheist.Net. Then I read this:

"If I told you that Jesus was a messianic wannabe prophet who preached certain moral principles around Jerusalem in the first century AD before being executed and buried then that sounds plausible based on what we know about that time period. If I then told you that the same Jesus physically rose from the dead and then ascended bodily into heaven then we know have a claim that goes directly against experience and common sense and it know warrants extreme skepticism."

In order to address what seems to me an unfortunate leap, let's back up to the stranger who offers a portal/tunnel at his house to the restaurant you are seeking. On the face of it this offer sounds absurd and you would surely be rational to dismiss the offer.

But then you discover that he is the director of CERN, the largest particle physics laboratory in the world. Suddenly the plausiblity of his offer has increased exponentially. Next, the famous physicist Steven Weinberg walks up, greets the director, and assures you that he does indeed have such a tunnel. By this point you may well be contemplating what, but moments before you would have dismissed without a second thought.

By the same token you cannot dismiss out of hand the testimony of the apostles because it is ALWAYS more plausible that a man who dies would stay dead. Rather, you need to look at the evidence. Maybe, just maybe, it could be true.