Comma before correlative conjunction not only ... but also

Question

I'm doing an ACT practice problem, and I'm confused.

In the sentence "Thousands of visitors from around the world travel to Siena during the summer, not only to witness the exciting race but also to attend the after-parties thrown by the locals." there is a comma before the not only. Why is there a comma?

The ACT's explanation is: "The second half of the sentence is an incomplete idea and must be linked to the complete thought." Note the question is asking whether there should be a comma before the not only.

If you were to remove the not only, I think the sentence would become "Thousands of visitors from around the world travel to Siena during the summer to witness the exciting race and to attend the after-parties thrown by the locals." In this case, the comma is removed, so why is there a comma when not only is added?

Answer 1

I do not accept the answer given.

Commas are frequently used where a brief pause would normally occur in speech. The “but also” phrase introduces what is intended to be a contrasting or at least a distinct thought. Such interpolations are usually marked off in spoken English by a brief pause; the comma usage follows.

You are correct that “X and Y” are not separated by a comma, nor are they separated by a pause in spoken English. The simple conjunction “and” indicates a single although compound thought that does not require a pause or comma.

I am not sure that one can give a reason for why English speakers view “to see … and to attend…” as a compound but single thought while viewing “not only to see …, but also to attend” as two distinct thoughts. They just do view the two phrases as being subtly different, and so speech patterns and recommended comma usage differ as well.

EDIT I failed to comment on the comma preceding “not only.”

I would punctuate the sentence as follows

Thousands … during the summer, not only to see …, but also to attend …

because those commas would be where I would pause slightly in expressing that complex a thought. It is not an unrelated thought but it is not as simple as

Thousands … during the summer [in order] to see … and to attend …

The implied “in order” is very common.

The “not only [in order] … but also [in order] …” is just perceived by most English speakers as requiring a pause to formulate by the speaker and to comprehend by the listener. It is not a typical flow of language.

Answer 2

Here the comma is optional. The part of the sentence (after the comma) is indicating purpose. The sentence being long, you may give a comma only for a pause.