I recently saw an episode of The Big Bang Theory, and they're a few lines of dialogue I don't understand. The lines are: Leonard: You don’t even understand what you did wrong because you can’t conceive of something that you are not an expert in! Sheldon: In which I am not an expert. Why is grammatically correct to say in which I'm not an expert?
Sheldon is pointing out that Leonard has stranded the preposition at the end of the sentence. More prescriptively minded grammarians eschew stranding prepositions. Leonard: You don’t even understand what you did wrong because you can’t conceive of something that you are not an expert in! Sheldon: In which I am not an expert. Preposition stranding is very common in idiomatic speech and whether one does or does not do this is, again, a matter of opinion and choice. The last example you gave: in which I'm not an expert in is not correct by any measure since you now have the preposition reduplicated.
Thanks for the quick reply! The last example is a mistake on my part. I was quoting Sheldon and accidentally added another in.
Understood. Then, yes, the little interchange between Leonard and Sheldon is about a grammatical quibble. One can find preposition stranding as far back as at least Shakespeare, probably further back. The word preposition literally means placed in front, so for many, the idea that the preposition can be divorced from and placed after the noun it is modifying feels wrong.
