This came up again when John Edwards said something like "it is me" and a talk show host said he was foolish and it should be "it is I", besides his transgressions of course. So I looked it up, and thanks for this blog.

While the academic information above and the linguistics comparisons to other language structures are great, I offer a middle of the road option that does not say that it just sounds better, but also does not get stuck in complex intricacies that may get away from the question perhaps and into pedantics that have apparently turned off some of the blog contributors.

Most (even highly educated) people don't delve into nominative, copulative, or other descriptors of a part of speech. I was previously taught something that has never let me down. If the sentence insinuates that "I" will be the person who acts in the second part of the sentence (such as "It was I who ate the pizza."), then I is a subject rather than object and is correct. (Of course who has to be thrown in and I know that will open up a whole other discussion as to whether "who" matters and "I" could be "me" instead).

If the placement of "I" is attempted at the end of a sentence, then what most people are looking for is simply a verb and subject structure of a basic sentence. Getting more complicated than that is the origin of why "It is I." sounds so snooty as described several times above. So in the same way that one might say "It is a piano.", one might say "It is me.", because "I" cannot be used as a subject in my understanding.

You could argue that one can say "The people on the first bus include Jen, John, and me.", rather than the other good option of "Jen, John and I will ride on the first bus." This all remains consistent (and much more sensible) to say whether you are using "I" in association with a verb, or whether "me" is used where there is no "me ride the bus" (which is why cookie monster sounds incorrect because he purposely is not using it correctly. The reason cookie monster is wrong is the same reason "it is I" is not my first choice, because "The sinner is me." is the same structure as "The roof is the shelter.", but using "Me like cookies." is the corollary of "Cookies are liked by I"... in other words, "me" can't like cookies but "I" can, and cookies can be liked by "me" but not by "I", depending on which is the subject of the sentence and therefore in which order the words appear; if me is used as a pronoun subject but I is used as the pronoun which performs the action of the sentence, it would be foolish to try using "I" at the end of a sentence of these forms).

As such, I'd like to respectfully disagree with the majority above, by saying that it is incorrect to say "Who is guilty? It is I.", but it is correct to say "It is I who am guilty." This can be explained by much simpler logic of nouns and subjects versus verbs, rather than the above complexities. I think the complexities above, although interesting, get away from the true usage of American English, where we are really looking to see whether "I" did something or not, and whether a list of subjects includes "me" (but cannot by rights include "I"). The reason is sounds better too, is because it is not some complex question, but rather a simple subject-verb structure of a phrase, and as such the simpler approach makes more sense to say "It is me."

Cheers