I'm having some trouble to classify the use of the to-infinitive and the -ing form of the verb in the following sentences:

"This problem has the potential to be really serious."

I took a look at links such as this, but no explanation seems to fit.

"Knowing what we know today, we could have made a different choice."

For this case, I refered to this link, but also didn't find a convincing classification. It seems like knowing would be a noun in that case? I'm not entirely sure. I would also like to know what is the "syntactic role" (not sure if this is the correct term) of "knowing" in the clause above. Is it a subject? An object? Sorry, it's very unclear to me because the structure of the clause is short-circuiting my brain.


EDIT: So, I figured out that the first example is an example of using the to-infinitive as a "postmodifier", as per this link. I still have no clue about how to classify the second sentence though. If anyone has a suggestion, it is greatly appreciated!

  • Actually, "I'm having some trouble to classify" has to be "I'm having some trouble (in) classifying" using the gerund not the infinitive. On the hand, if you had said "I'm finding it hard to classify" then that one has to take the infinitive not the gerund. Because English uses both kinds of non-finite verb forms as nominal elements like subject—but which has to be used where varies by verb/predicate frame, it's much harder than in languages like Spanish where only the infinitive can be a subject or object and the adverbial gerund is reserved to modifier roles or continuous "tenses".
    – tchrist
    Commented Jun 11, 2022 at 20:22
  • Thanks for the observation @tchrist! I actually solved part of the problem myself. In this link it is explained that the first usage is an example of a postmodifier! I'm still not sure about the second sentence I provided though. Commented Jun 11, 2022 at 21:29
  • 2
    The second link is a fronted participial phrase, like Standing on the corner, there was a lamppost. Whether to use an infinitive or an ing form depends on the predicate (adjective, noun, or verb) and also on what construction it's being used in. Both of them can occur as subjects (with some verbs), objects (with some verbs), and objects of prepositions. And they occur also in all kinds of constructions, like going to V, have to V, like Ving/to V, enjoy Ving, want to V, etc. There are also purpose infinitives like He stopped to smoke. Commented Jun 11, 2022 at 21:45
  • @JohnLawler thank you so much sir! Your answer was very helpful. In that case then, "knowing" is not a gerund, but a Present Participle, is that correct? In this case, would it be an adjective in the sentence that I exemplified? Commented Jun 11, 2022 at 22:07
  • 1
    The most important point for Spanish and Portuguese speakers is to learn to use gerund nouns as subjects: Surfing is fun. The second (for intermediate learners) is to learn when you can use V + ing versus V + to. That is: I like to play tennis. and I like playing tennis. are the same in everyday speech (but not for picky grammarians). verbs of liking/disliking such as like, hate, love, dislike can go both ways. Whereas "enjoy" or "detest" cannot "take" to. And there's more of that lurking around, too.
    – Lambie
    Commented Jun 12, 2022 at 16:33

1 Answer 1


[1] This problem has the potential [to be really serious].

[2] [Knowing what we know today], we could have made a different choice.

"Be" and "knowing" are both verbs.

In [1] the infinitival clause is a complement licensed by the noun "potential".

In [2] the gerund-participial clause is an adjunct in clause structure, more specifically an adjunct of 'implicated reason': it can be interpreted as giving the reason for the matrix situation.

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