I am bit perplexed as to the function of the infinitive subordinate clause in the following examples:

I know him to be a good man.

I persuaded him to leave.

In analyzing this sentence, "know" seems to be of complex transitive pattern, which suggests that the constituent [to be a good man] could be an object complement. The constituent's offering some allusion to the object (him) also corroborates the assumption of [to be a good man] being an object complement.

However, according to my understanding -- and I believe this to be the most consistent analysis, the object complement is always either an NP or AP. That is, the only constituent that alludes to the direct object "him" is "a good man" and not "to be a good man" . This fact coupled with infinitive clauses sometimes having an overt subject prompt me to think that the infinitive clause is [him to be a good man], and that the latter functions as a direct object of the verb "know".

Which analysis is the most correct ?

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    – tchrist
    Jan 7, 2023 at 18:55

2 Answers 2


[1] I know him [to be a good man].

[2] I persuaded him [to leave].

No: the bracketed infinitival clauses are not object complements. Object complements are almost always NPs or AdjPs, not normally clauses.

They are catenative clauses functioning as complements of the catenative verbs "know" and "persuaded".

In both examples, the intervening NP "him" is the syntactic object of the matrix verb, and the understood (semantic) subject of the subordinate clause.

Note that semantically in [2] "him" is an ordinary object, but in [1] it is a raised object because the verb that "him" relates to syntactically is higher in the constituent structure than the one it relates to semantically.


You're right about a lot of it, but you chose the wrong constituents. To be a good man is not a complement; it's an infinitive verb phrase. Verbal infinitive object complements are full clauses, and thus have both infinitive subject noun phrases and infinitive verb phrases.

Exactly how they work depends almost entirely on what the main verb is; here the examples are know and persuade.

  1. I know [him to be a good man].
  2. I persuaded [him to leave].

I've bracketed the object complement clauses. It turns out that both clauses have him as subject (subjects of infinitives are in the objective case), and both of these subjects lack the for subject complementizer that occurs occasionally

  • For him to be elected would be a surprise.

though all of the verb phrases have the characteristic to infinitive verb phrase complementizer. (This is why infinitive complements are also called for-to complements, and gerunds POSS-ing.)

These two clauses are different, however, because the him of (1) is a raised subject (i.e, not only is it the subject of be a good man, it's also become a passivizable object of know -- it can be passivized, for instance:

  • He is known (by me) to be a good man.

Whereas persuade is a verb of communication with an indirect object -- there has to be somebody that gets persuaded. So (2) means the same as

  • I persuaded him that he should leave.

which has two references to him -- once as persuadee, and once as leaver. So the NP has a role in both clauses, and gets deleted in the complement. This is called Equivalent Noun Phrase Deletion, or "Equi" for short. Both Raising and Equi are common in English and characterize many verbs and their untensed complements.

It's interesting to contrast Equi and Raising verbs. Some of the tests are especially fun:

  • The shit has been known to hit the fan there pretty often.
  • There is known to be a party somewhere on this floor.
  • *The shit has been persuaded to hit the fan there pretty often.
  • *There has been persuaded to be a party somewhere on this floor.
  • Thank you @John, what I wanted to clear out is where is the subordinate clause: is it just [to be a good man] whether the infinitive clause [him to be a good man] and [him to leave] are functioning as Direct Object ? In Bill J's answer he said that they are catenative verb complements,
    – Med Jr
    Jan 8, 2023 at 17:28
  • That depends on what stage of the derivation you're looking at. Lemme give a simpler example: In an imperative, is the full sentence/clause Go to bed or is it You go to bed? In other words, how are you defining "clause" today? Does it hafta have a subject? If not, all other English sentences and most other English clauses are irregular; if so, then you hafta provide the subject and present reasons why it should be You and not something else. Jan 8, 2023 at 17:33
  • My ultimate purpose is to draw a tree diagram. Towards this end, I need to know the nature and function of the constituents in question. We have studied that Non-finite, infinitve clauses may or may not have subjects, so i am wondering if it is correct to consider [him to be a good man] and [him to leave] as direct objects of the main verbs.
    – Med Jr
    Jan 8, 2023 at 17:39
  • in imperative cases, we call the subject an empty subject that is implied
    – Med Jr
    Jan 8, 2023 at 17:40
  • We don't do tree diagrams here; they're only sketchy terms for instruction, and they don't follow regular rules. Ask your syntax instructor how to handle terms that are implied and how to tell them from terms that aren't. No one cares about tree structures except syntax teachers. They are of no use for any other purpose than visualizing certain cases of syntax (and not others) using certain theories of syntax (and not others). Jan 9, 2023 at 15:38

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