Is "sitting" a participle, gerund, or adjective in the sentence, "I saw him sitting."

Question

I have having trouble explaining to someone why, in a past tense sentence, the second verb is sometimes in the present tense. Here is the sentence:

I saw him sitting.

I know the sentence is grammatically correct as written, but why does "sitting" assume the form it does?

I have tried looking this up on numerous grammar sites and in more academic texts, such as Garner's "The Chicago Guide to Grammar, Usage, and Punctuation." It seems that "sitting" is either an adjective, gerund, or present participle.

If I rephrase the sentence, it becomes clear how "sitting" acts as:

...an adjective: I saw the sitting man.

...or a gerund: Sitting is his favorite hobby.

...or a present participle, as with the progressive tense: I saw that he was sitting.

But I can't determine what function "sitting" has in the original sentence, I saw him sitting.

Thank you for your help!

Answer 1

Most modern grammars don't distinguish between "participle" and "gerund". And this gives a good example of why.

This isn't an adjective. It is certainly a verb. You could ask, sensibly, about the subject of this word, and agree that it is implicitly "him". So this word does head a clause and so it is a verb.

Hence it is a gerund-participle.

It forms an object complement.

Now the distinction (as claimed) between gerunds and participles is that gerunds function "as nouns", and participles function "as adjectives or adverbs". But the object complement can be a noun phrase, or an adjective. So this gives a good example of why you can't distinguish between gerunds and participles on the basis of what they function as.

In conclusion, this is an object complement formed from a participle/gerund clause consisting of a single word.