A colleague of mine asked me the other day how best to explain the word learn in this sentence: They looked for a good school for a long time, so they’re pleased now to see their child learn so much so quickly. It’s a good, sturdy sentence, and, in fact, the form of the verb learn is just what gives it a slight sense of formality. But the subject of the verb learn is the singular noun child, so why isn’t the verb in the singular form learns?
Let’s begin by comparing this second half of the sentence to another, more casual way of saying the same idea: so they’re pleased now to see that their child is learning so much so quickly. In this version, the verb learn has been converted into the form is learning, and there we can see that the noun child now does work with a singular verb, the word is in the expanded verb phrase is learning. The difference between these two versions, to see their child learn and to see that their child is learning, lies in the object of the verb see: in the first the object is a phrase, and in the second the object is a clause.
We know that a clause is a group of words with a subject and a verb, but we should understand that the verb of a clause stands in what is called its finite form. Something finite is something specific, and so a finite verb is specific as to its subject, number, and tense—all the things that go into making a real predicate and the scene of some action. The finite forms of a verb are what we know as its conjugated forms, the changes a verb undergoes as its subjects and time change. A child learns, for example, but children learn, whereby we put the letter s on the verb to signal a singular subject, and omit it for the plural. We know too that clauses can be independent or subordinate, and that we can recognize the difference by noting the conjunction with which a particular clause begins. In the clause that their child is learning, the word that is a subordinating conjunction, and it functions to make the entire group of words it initiates into a noun. Nouns can stand as objects of verbs, and so the entire subordinate clause that their child is learning is the object of the verb see in our second, more casual version.
Things are very different in the first, original style. To write that they are pleased to see their child learn, the verb learn remains in its infinitive form, that is, a nonfinite construction. While it’s true that infinitives have time, they don’t have person or number. That means they are not as specific as their corresponding finite forms, and that they cannot therefore present a predicate, a scene of action, on their own. Infinitives create phrases, not clauses, and in doing so, they leave the real action to some other verb they’re working with. In our example, that’s the verb to see.
Now here’s where this particular sentence gets interesting, because to see is an infinitive in its own right. It looks back to the finite verb are pleased, and so this section of the sentence unfolds with two infinitives after a finite verb: pleased to see their child learn. The first infinitive, to see, answers how it is that the parents are pleased, and the second infinitive, learn, along with its subject child, shows what it is the parents saw. Verbs of perceiving or thinking can build what are called indirect statements, and in such constructions, the subject (in the objective case) is paired with the infinitive form of the verb, not the finite. So, to see their child learn, not to see their child learns.
All this grammar gives us a choice, and that’s just the point of understanding sentence structure. Grammar works complementarily with style, or rhetoric, and the two (along with some critical thinking) together take on many different shapes and possibilities, some more appropriate to a particular audience than others in getting our ideas across. It’s ours to understand and decide.
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