I’ve heard the word incredulous attributed to situations, as in That’s an incredulous story. The problem is that incredulous means skeptical or disbelieving, which is a human trait, not something that can be attributed to an inanimate object, a theory, or a situation. I was incredulous of his story (I was skeptical of his story) is the correct use of incredulous.
Incredible means not to be believed, as in That’s an incredible story (a story that’s difficult to believe).
Here are other examples:
- He looked at me with an incredulous stare. (a stare of skepticism)
- I was incredulous of his request. (disbelieving of his request)
- The details of his excuse were incredible. (the details were unbelievable)
Oh, I can hear it now: Didn’t Shakespeare use incredible to mean incredulous at some point in his writings? Ergo, doesn’t that mean that incredible and incredulous are synonymous?
In a word—-no. And considering the common belief by scholars that he had a very limited education, it shouldn’t be surprising. Shakespeare may have written some insightful works, but that doesn’t necessarily mean he had a perfect command of vocabulary or that we should give absolute deference to his grammar skills. None of us can boast such perfection, and, really, who would want to? It’s too much of a burden.