In modern grammar, why are gerunds and participles grouped?

Question

As I have delved deeper into the world of modern grammar, I have noticed frequent references to 'gerund-participial' clauses. Most resources would divide gerunds and participles (past and present) into their own categories, stating that they have different functions. Notably, a gerund can act as a subject or object, whereas a participle cannot. However, I have not seen an accompanying explanation as to why modern grammarians have stopped making the distinction.

I have accepted this new categorisation, but I don't fully grasp the reasoning. Could someone who is knowledgeable about modern grammar explain?

Answer 1

From Language Log

...I was happy when Geoffrey Pullum and Rodney Huddleston, in the Cambridge Grammar of the English Language, presented a clear and compelling argument that "A distinction between gerund and present participle can't be sustained" (pp. 80-83 and 1220-1222). They therefore use the merged category "gerund-participle". I hope that most of you will be as happy about this development as I was. The core examples of the present participle are its uses as a modifier or predicative in sentences like those given in CGEL 3 [14]:

The train is now approaching Platform 3.

The train approaching platform 3 is the 11.20 to Bath.

He threw it in the path of an approaching train.

The core examples of the gerund are its uses as the verbal head of a noun-like construction in sentences like those in CGEL 3 [19]:

Destroying the files was a serious mistake.

I regret destroying the files.

CGEL:

Historically the gerund and present participle of traditional grammar have different sources, but in Modern English, the forms are identical. No verb shows any difference in form in the constructions of [14] and [19], not even be. The historical difference is of no relevance to the analysis of the current inflectional system […] This grammar also takes the view that even from the point of view of syntax (as opposed to inflection) the distinction between gerund and present participle is not viable, and we will therefore also not talk of gerund and present participle constructions […]

Answer 2

In comments John Lawler wrote:

It's a matter of terminology. "Gerund" and "participle" are both words that describe specific Latin constructions -- quite a few of them, in fact, because Latin had more participle types than English does, so that Latin grammarians considered participles as being their own part of speech -- not verbs. Today we talk about English participles and gerunds as if they were separate things, like the Roman grammarians did (to them, gerunds were verb forms, not participles). But actually English gerund constructions are just one use of the present participle form and that's where "gerund/participial" comes from.

We know that English verbs have two participial forms -- the {-EN} "past participle", like tired, worn, finished, shelled, etc, and the {-ING} "present participle" like tiring, wearing, finishing, shelling, etc. They all come from verb forms and there's only two such forms; but each one has dozens of uses, some of which have strange names with strange histories in other languages. So we use scare quotes around the terminology.

Answer 3

In a comment Araucaria wrote:

Well, in short, you’ve already put your finger on it! There’s no other type of word which we assign to different categories according to its grammatical relations. So a noun is a noun whether used as a subject, object, determiner, modifier and so forth. In modern English, calling the -ing form of a verb a participle or gerund just tells us what its grammatical relations are and tells us nothing meaningful about what type of word it is!