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Bracketing Commas

Bracketing commas (also called isolating commas) do a very different job from the other three types. These are the most frequently used type of comma, and they cause more problems than the other types put together. The rule is this: a pair of bracketing commas is used to mark off a weak interruption of the sentence — that is, an interruption which does not disturb the smooth flow of the sentence. Note that word `pair': bracketing commas, in principle at least, always occur in pairs, though sometimes one of them is not written, as explained below. Look carefully at these examples of bracketing commas:

These findings, we would suggest, cast doubt upon his hypothesis.
Schliemann, of course, did his digging before modern archaeology was invented.
Pratchett has, it would seem, abandoned Rincewind the wizard to the ravages of the Discworld.
Darwin's Origin of Species, published in 1859, revolutionized biological thinking.
The Pakistanis, like the Australians before them, have exposed the shortcomings of the England batting order.
Rupert Brooke, who was killed in the war at the age of 28, was one of our finest poets.
We have been forced to conclude, after careful study of the data, that the proposed correlations, in spite of their obvious appeal, do not stand up.
In each case a weak interruption has been set off by a pair of bracketing commas. (The last example has two weak interruptions.) Now notice something important: in every one of these examples, the weak interruption set off by bracketing commas could, in principle, be removed from the sentence, and the result would still be a complete sentence that made good sense. Try this with some of the examples:
These findings cast doubt upon his hypothesis.
Pratchett has abandoned Rincewind the wizard to the ravages of the Discworld.
The Pakistanis have exposed the shortcomings of the England batting order.
We have been forced to conclude that the proposed correlations do not stand up.
This is always the case with bracketing commas, and it gives you a simple way of checking your punctuation. If you have set off some words with a pair of bracketing commas, and you find you can't remove those words without destroying the sentence, you have done something wrong. Here is an example of wrong use, taken from Carey (1958):
*Yet, outside that door, lay a whole new world.
If you try to remove the words outside that door, the result is *Yet lay a whole new world, which is not a sentence. The problem here is that outside that door is not an interruption at all: it's an essential part of the sentence. So, the bracketing commas shouldn't be there. Just get rid of them:

Yet outside that door lay a whole new world.
Here is another example:
*She groped for her cigarettes, and finding them, hastily lit one.
This time, if you try to remove the words and finding them, the result is *She groped for her cigarettes hastily lit one, which is again not a sentence. The problem is that the interruption in this sentence is only the sequence finding them; the word and is not part of the interruption, but an essential part of the sentence. So move the first comma:
She groped for her cigarettes and, finding them, hastily lit one.
Now check that the interruption has been correctly marked off:
She groped for her cigarettes and hastily lit one.
This is a good sentence, so you have now got the bracketing commas in the right places.

Since bracketing commas really do confuse many people, let's look at some further examples:

*Stanley was a determined, even ruthless figure.
What's wrong here? Well, that comma can't possibly be a listing comma, a joining comma or a gapping comma; therefore it must be intended as a bracketing comma. But where is the interruption it is trying to bracket? It can't be the three words at the end: *Stanley was a determined is so much gibberish. In fact, the weak interruption here is the phrase even ruthless, and the bracketing commas should show this:
Stanley was a determined, even ruthless, figure.
This is perfect, since now the bracketed interruption can be safely removed:
Stanley was a determined figure.
Sometimes this very common type of mistake will not disturb your reader too much, but on occasion it can be utterly bewildering:
*The Third Partition of Poland was the last, and undoubtedly the most humiliating act in the sorry decline of the once-powerful kingdom.
Here the sequence before the comma, The Third Partition of Poland was the last, seems to make sense by itself, but unfortunately not the sense that the writer intends. With only one comma, the reader will surely assume the writer means `The Third Partition of Poland was the last [partition of Poland]', will go on to assume that the word undoubtedly begins another statement, and will be left floundering when she abruptly comes to a full stop instead of a verb. The essential second bracketing comma removes the problem:
The Third Partition of Poland was the last, and undoubtedly the most humiliating, act in the sorry decline of the once-powerful kingdom.
Here is another example of a type which often causes trouble:
The people of Cornwall, who depend upon fishing for their livelihood, are up in arms over the new EC quotas.
As always, we could in principle remove the bracketed interruption to produce a sensible sentence:
The people of Cornwall are up in arms over the new EC quotas.
But note carefully: this sentence is talking about all the people of Cornwall, and not just some of them, and hence so was the original sentence. The weak interruption in the original sentence is merely adding some extra information about the people of Cornwall. Now consider this different example:
The people of Cornwall who depend upon fishing for their livelihood are up in arms over the new EC quotas.
This time their are no bracketing commas because there is no interruption: now we are not talking about all the people of Cornwall, but only about some of them: specifically, about the ones who depend upon fishing for their livelihood. Here the phrase who depend upon fishing for their livelihood is not an interruption but an essential part of the sentence, and hence it receives no bracketing commas.

Sometimes a weak interruption comes at the beginning or at the end of its sentence. In such a case, one of the two bracketing commas would logically fall at the beginning or the end of the sentence — but we never write a comma at the beginning or at the end of a sentence. As a result, only one of the two bracketing commas is written in this case:

All in all, I think we can say that we've done well.
I think we can say that we've done well, all in all.
When the weak interruption all in all comes at the beginning of the sentence, it has only a following comma; when it comes at the end, it has only a preceding comma. Compare what happens when the interruption comes in the middle:
I think we can say that, all in all, we've done well.
Now the interruption has two bracketing commas. Regardless of where the interruption is placed, it could be removed to give the perfectly good sentence I think we can say that we've done well.

Here are some further examples of weak interruptions that come at the beginning or at the end.

At the beginning:

Having worked for years in Italy, Susan speaks excellent Italian.
Unlike most nations, Britain has no written constitution.
Although Mercury is closer to the sun, Venus has the higher surface temperature.
After capturing the Aztec capital, Cortés turned his attention to the Pacific.
And at the end:
The use of dictionaries is not allowed, which strikes me as preposterous.
The pronunciation of English is changing rapidly, we are told.
The Rose Parade is held in Pasadena, a suburb of Los Angeles.
Once again, the words set off by a single bracketing comma in these examples could be removed to leave a good sentence. Check this for yourself.

There are a number of common words which typically introduce weak interruptions containing complete sentences. Among the commonest of these are although, though, even though, because, since , after, before, if, when and whenever. Weak interruptions introduced by these words are usually rather long, and therefore they most often come at the beginning or at the end of a sentence. Some examples:

Although Australian wines are a fairly new phenomenon, they have already established a formidable reputation.
After the Roman legions withdrew from Britain, the British found themselves defenceless against Irish and Viking raids.
If there are any further cuts in funding, our library will be severely affected.
Hitler could never have invaded Britain successfully, because their excellent rail system would have allowed the British to mass defenders quickly at any beachhead.
Columbus is usually credited with discovering America, even though the Vikings had preceded him by several centuries.
There is just one case in which you might find yourself apparently following all the rules but still using bracketing commas wrongly. Consider the following example, and try to decide if the comma is properly used:
Note that in each of these examples, the material set off by commas could be removed without destroying the sentence.
The comma in this example is clearly not a listing comma, a joining comma or a gapping comma. Is it a bracketing comma? Try removing the words before the comma:
The material set off by commas could be removed without destroying the sentence.
This appears to be a good sentence, and so you might think that the original example was correctly punctuated. But it is not. The problem is that the original sentence was an instruction to notice something, and the words Note that are therefore an essential part of the sentence, not part of the interruption. The interruption, quite clearly, consists only of the words in each of these examples. When we tried to remove the first seven words, we got something that was a sentence, purely by accident, but a sentence in which the original meaning had been partly destroyed. The original attempt at punctuating was therefore wrong, and it must be corrected by adding the second bracketing comma around the interruption:
Note that, in each of these examples, the material set off by commas could be removed without destroying the sentence.
Now the interruption marked off by the bracketing commas can be safely removed without wrecking the sense of the sentence:
Note that the material set off by commas could be removed without destroying the sentence.
Therefore, when you are checking your bracketing commas, make sure that the words enclosed in commas really do make up an interruption, and do not include an essential part of the sentence.

In many cases a weak interruption does not absolutely require bracketing commas. Thus either of the following is fine:

Shortly before the war, he was living in Paris.
Shortly before the war he was living in Paris.
With or without the bracketing comma, this sentence is perfectly clear. Sometimes, however, the bracketing comma is absolutely essential to avoid misleading the reader:
*Just before unloading the trucks were fired upon.
Here the reader naturally takes Just before unloading the trucks as a single phrase, and is left floundering as a result. A bracketing comma removes the difficulty:
Just before unloading, the trucks were fired upon.
The best way to avoid problems of this sort is, of course, to read what you've written. Remember, it is your job to make your meaning clear to the reader. The reader should not have to struggle to make sense of what you've written.

Here are the rules for using bracketing commas:

• Use a pair of bracketing commas to set off a weak interruption which could be removed from the sentence without destroying it.
• If the interruption comes at the beginning or the end of the sentence, use only one bracketing comma.
• Make sure the words set off are really an interruption.