Whether you call it a serial comma or the Oxford comma, mentioning it is bound to stir up a debate – and since Chicago Manual of Style recommends that extra comma in a series and the AP Stylebook does not, the sides often break into book editors vs. newspaper and magazine editors.
Why does it matter? Why can’t we just pick one and stick with it? As simple as that seems, there are instances where one solution really is better.
This is a classic example pro-Oxford folks use:
The most influential people in my life have been my parents, the Pope and Indira Gandhi.
Wow! Your parents are the Pope and Indira Gandhi? Wait – the Pope has children? The silly thing about this example, of course, is that everyone knows the Pope and Indira Gandhi didn’t have any children together. Adding the serial comma will clear up any initial confusion before clarity and common sense kick in.
A more realistic example is the following, from the AP Stylebook:
I had orange juice, toast, and ham and eggs for breakfast.
This is a complex series, and that extra comma makes for better comprehension. As with all matters of style, the most important thing is to be consistent — but be flexible enough to bend the rules if it means your readers will understand your meaning right away.