Is It "my friend and I" or "my friend and me"?

I live in Spain, and in order to strengthen our connection, every day I email my mother, who still lives in the United States. Today I received a message from her that inspired the following... rant:

I texted Urraca to invite her to lunch on Thursday here with Elvira and I.

After a couple of other sentences, she used parentheses to ask me, a professional editor, about a grammar point:

(Jessica, is it "Elvira and I" or "Elvira and me"? The computer keeps telling me it's "me." I prefer "I.")

Kudos to my mom, because AI grammar aids aren't yet sophisticated enough to fathom all the possible kinks in English grammar and the creative expressions of its speakers. Many times, AI advice on these issues is just plain wrong.

For the TL;DR crowd: In this case, "the computer" is right. "Elvira and me" is "right," and the preferred *"Elvira and I" is "wrong."

There are, of course, some cases in which "Elvira and I" is correct. Scroll to the end for a simple trick to help you decide which phrase to use.

I love language history, so I can't resist explaining why "Elvira and me" is correct here and maybe not elsewhere.

Natural languages are in constant evolution. Thousands of years ago, Indo-European languages (the family that includes English) had hardly any prepositions, coupled with looser word-order requirements. So how did ancient people explain the relationship between the nouns in a sentence?

One ancient Indo-European language for which we have abundant examples, Classical Latin, used declensions. In Latin, these were word-endings. There were, basically, six possible word-endings, and they showed the relationship between the nouns so well that the most frequent sentence structure is a string of nouns with a verb at the end (conjugated to match the only noun in the sentence declined in the nominative case, if you want that kind of detail). The famous simple example:

Nero Agrippinam occidit.

(Nero killed Agrippina.)

(You might assume Classical Latin is boring, but in reality, very few boring sentences in that language have survived to the present.)

The verb at the end matches Nero, who is in the nominative case and therefore the actor in, or subject of, the sentence. The "m" at the end of Agrippina marks her as being in the accusative case, the object or receiver of the action.

Modern English shows this relationship strictly with word order. How did we get here?

Prepositions (to, in, by, with, etc.) were invented long, long ago to emphasize or clarify relationships between nouns that might've been a bit ambiguous with just declensions.

By the time the Middle Ages rolled around, 1500 to 1000 years ago, Latin had evolved to use prepositions much more frequently, the Romance languages were slowly being born, and writers started to abandon declensions.

We don't have evidence of written English from the same time period as Classical Latin, but we do have some stunningly beautiful examples from the beginning of the Middle Ages, known as Old English. Old English uses an average of four different declensions with a full array of prepositions also required.

The way Latin and English coincide in their use of prepositions and declensions at this time suggests that at one time in the past, English or its ancestor used even more declensions and fewer prepositions, i.e., that its evolution in this respect has been very similar to Latin's.

Follow this evolution into Modern English, and we have almost no declensions for our nouns at all. (Remind me to tell you about the Old English genitive in Modern English some time.)

But we do still have declensions for our pronouns!

To continue using my mom's example, the declensions of the first-person pronoun are:

I (nominative case, the actor, the subject)

me (accusative/dative/ablative cases, the acted upon, the object)

my (genitive case, possessive)

The general rule is that if you're using a preposition, what follows is an object and not in the nominative case.

Because my mom uses the preposition "with" to indicate that she and her friend will be "here" at the same time as the people who are being invited, she and her friend are being acted upon (the objects) and cannot be in the nominative case. It wouldn't make any grammatical sense! Therefore, the correct solution is to use the accusative/dative/ablative case and write "with Elvira and me."

Note that Elvira, being a noun and not a pronoun, can no longer be declined in the accusative/dative/ablative case. Nouns have evolved to appear to be practically always nominative. This is probably the root of the confusion over this issue, which is widespread.

I hear people using phrases like *"with Elvira and I" all the time (on TV, mostly, because I live in Spain) and read this phrase all too often on the Internet and in the books I edit.

Young children who acquire English as their first language often go through a phase in which they say things like *"Me want juice." This flipside of this issue is another result of declensions having become nonintuitive to modern people.

Various people throughout history must've thought *"Elvira and I" sounded more elegant or even (erroneously) more correct. It started out slowly, and with the incredibly fast circulation of information that is our normal, it gained momentum to the point that the formation has calcified for some people. These are people, like my mom, who "prefer Elvira and I."

Faced with a situation of ownership, some of these people have come up with the solution *"Elvira and I's house."

The word *"I's" is horrible. Please don't use it when we have the perfectly serviceable "my." Yes, "Elvira and my house"! Try it!

As I mentioned, natural languages are in constant evolution. Honestly, a reality in which the remnants of declensions in pronouns, so me, him, her (accusative/dative/ablative), and poor old whom disappear, and *"Elvira and I" becomes always correct looks like a next step for English.

But for now, while we still have me as an option:

Simple trick to decide if it's me or I:

Mentally remove the interfering noun and keep the pronoun:

lunch here with Elvira and I -->

lunch here with I.

Sounds wrong, doesn't it? That's because it is. In this case, it's "with me," therefore:

lunch here with Elvira and me.

In the other case, it's even easier, because the pronoun comes at the beginning of the sentence, and the noun isn't in the way:

Elvira and I went to the movies.

That's clearly correct (because the pronoun has to be in the nominative case in order to be the subject of the following verb). Easy! (Please request clarification if this isn't as easy as I think.)

Thanks for reading! All best for your writing endeavors.