Q: I am a retired English teacher, and I have been tutoring a Korean boy. His mother is also interested in learning English, and she asked me this question. In the sentence “I laughed when I saw her fall,” why is the verb “fall” and not “fell,” since “laughed” is in the past tense? I posted this question on a grammar forum, but no one has responded. Can you enlighten us?
A: In the clause “I saw her fall,” the verb “fall” is in the infinitive: the simple, uninflected form of a verb. (A clause, as you know, is a group of words with its own subject and verb.)
In English, this is a very common pattern: one verb followed by a second in the infinitive. It’s often the case when the first verb is one involving sensory perception (“see,” “feel,” “hear”).
Here are a few examples of the kinds of verbs that are often paired with infinitives (the infinitives are underlined):
“I helped her walk” … “They saw us go” … “We felt it move” … “He heard her cry” … “You need not worry” … “Dare we ask?” … “I would rather die” … “We will let it rest” … “Let there be light.”
In addition, the auxiliary “do” is often used with an infinitive to form a question: “Do you smoke?” … “Did they drive?”
And the modal auxiliary verbs (“can,” “may,” “must,” etc.) take infinitives as their complements: “She may smoke” [or “May she smoke?”] … “We must leave” [or “Must we leave?”].
In all of these cases, the second verb is in the infinitive because it needs no inflection. (An inflected verb changes in form to indicate number, tense, and so on.)
Many people don’t recognize these verb forms as infinitives because they expect infinitives to be preceded by “to.” As you can see, that’s often not the case.
Even when the “to” is present, it’s not actually part of the infinitive. It’s a prepositional marker indicating that the infinitive is coming up. So you can’t “split” an infinitive, no matter what anyone tells you. We’ve written before on the blog about the “split infinitive” myth.