What is the grammatical difference between I and me or we and us? Or I and my or we and our? All of these forms (and many more) have to do with what is called grammatical person and number. We are all familiar with the forms, but perhaps not with the topic to the degree we would otherwise wish. Here’s a quick review.
The term grammatical person refers to the fact that our everyday language tries to replicate the three-dimensional world we are alive within—at least as our minds construct it—and to find meaning and ideas within that same world of dimensions. English recognizes three persons (and that term extends to inanimate things as well), and calls them first, second, and third: the first person refers to the person speaking, the second person to the person spoken to, and the third person, the person spoke about. One difference between I and you and he (or she or it), then, is just that: first, second, and third person, respectively.
With this idea of grammatical person is associated the further idea of grammatical number. English recognizes two numbers, singular and plural, and so each singular grammatical person has its form to point to its corresponding plural: I and we, you and you, he (or she or it) and they. The person speaking, for example, may be either one or many, and so grammar refers to the first person singular or first person plural, and it does the same with the second and third persons. This is why we can refer to the narrative voice of a novel, for example, as written in the first person or third person (and there are examples of second person too). The singular number is usually assumed, but the singular person might be omniscient as well, meaning the narrator of the story knows what the characters might not.
Now there is another feature of these forms called case, which explains the further difference between I and me or we and us, together with many others forms as well (all the forms we are considering here are called personal pronouns). The term case refers to the way the grammatical function of a word in a sentence is expressed in either spelling or position. English works with three cases, and each has a set of grammatical functions it serves: the nominative case indicates the subject of a verb, the possessive case points to the possessor of something, and the objective case shows the object of a transitive verb or preposition. So, for example, we would analyze the pronoun they in the sentence They went to Los Angeles last week as third person plural, nominative case. In the sentence Their luggage was lost, the pronoun their is understood to be third person plural, possessive case (note the difference in spelling between the possessive pronoun their and the adverb there). And in the sentence I spoke to them the day they returned, the pronoun them functions as third person plural, objective case, as object of the preposition to.
This last example points to an especially frequent mistake in modern English, which we probably hear more often than we see written. The objective case, as we’ve noted, marks the object of both a transitive verb and of a preposition. Every preposition has an object (the two forming a prepositional phrase), and that object must (according to the traditional rules, as least) take the objective case. So we say to them, not to they. But we will often hear sentences like That’s the difference between you and I or She spoke to he and I about it yesterday. These are incorrect because both between and to are prepositions, and so should govern (as the traditional term has it) the objective, not nominative, case.
It’s not so much a matter of slavishly following rules as it is of honoring the integrity of the craft as it comes to us that all these observations apply. Change is both good and inevitable, but change must have its reasons as well.
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