The Law of False Attraction

It's not I, it's me.

Some time ago, I wrote a short article about the parts of a sentence (see Subject, Predicate, Object). Slightly later (see What's a Case?) I mentioned that the nominative is the case that names something—often the subject of a sentence. When I say I wrote a short article about the parts of a sentence, the subject (the nominative) is I. The predicate (the part that declares something about the subject) is the rest of the sentence: wrote a short article about the parts of a sentence. Usually, the predicate involves a verb about doing something (writing, for example) and sometimes a direct object (a short article) or an indirect object (the parts of a sentence).

Lots of sentences work this way, but not all do, because not all verbs are about action. A copula, or linking verb, shows a relationship between two ideas. Naomi is a baker, for example, or You look happy.

In the latter sentence, the predicate look happy consists of¹ a linking verb and an adjective called the predicate adjective. Verbs like feel, seem, or smell are useful for connecting the subject nominative with a descriptive predicate adjective.

In the former sentence, the predicate has—wait for it—another nominative. Verbs like be and become are useful for linking two nominatives to show that they both name the same thing. Naomi is a baker—better yet, Naomi is the baker in this story—makes it clear that when we talk about Naomi, we're talking about a baker. This is called a predicate nominative. The predicate (what we're declaring about the subject) names its other identity.

We all know that the verb must agree with the subject in both number and person. We can't say *Naomi are a baker (wrong number) or *Naomi am a baker (wrong person). Naomi is singular and we're addressing them in the third person, so we say Naomi is a baker.

So what happens when the predicate nominative doesn't agree with the subject? If you say Naomi's cakes are her strength, it sounds natural. Why is it not *Naomi's cakes are her strengths or *Naomi's cakes is her strength? If you swap nouns, you run into similar problems: Naomi's strength is her cakes sounds right, but *Naomi's strength are her cakes doesn't work at all.

This problem is called false attraction to the predicate nominative.² When you use a copula to equate two things, they don't have to agree. We say woe is me and not woe am I. If Naomi arrives with a delivery of cakes, it's more natural to say it's her than it's she. When subject and predicate nominatives disagree in number, we stick to the rule of subject-verb agreement and don't worry about the predicate nominative.  

1. Sure, comprises. Whatever.

2. Or, as the Chicago Manual of Style calls it, False Attraction to a Predicate Noun.