Once upon a time – actually it was only 50 years ago – two merry widows shared an elegant flat in Richmond, Va. Lucy and Millicent were Episcopal ladies of a certain age. Understandably, they took an Episcopal view of life’s little pleasures.

One January, as the Lenten season approached, they agreed upon their penance. It was Millie’s idea, but Lucy concurred. This was their pact: During the 40 days of privation that lay ahead, “we will not have a drink unless we really need one.” In a state of benevolent grace they lived well into their 90s.

The dear ladies came to mind the other day when Constant Reader wrote me a letter of serious reproach. He was dismayed by my “continuing cavalier disregard” for the Rule of the Serial Comma. This is a supposed rule for writers. It commands that in a series of discrete elements, the final element must be separated by a comma from the elements that precede it. Thus, “A healthful menu includes daily servings of Wheaties, Cheerios, Grape Nuts, Rice Krispies, and Corn Flakes.” Without a cereal (cq) comma after “Rice Krispies,” everything supposedly is mush.

Millie’s Rule applies to Constant Reader’s complaint. In serial constructions, let us never use a final comma unless we really need one. Except for blind adherence to a rule book, nothing commends a comma after “Rice Krispies.” The sentence is abundantly clear without it. And there is this further consideration: Punctuation marks are important to the pace, or flow, of prose composition. Commas will slow things down, as in the commas that just muffled “flow” a moment ago. Punctuation marks are our road signs. An em-dash signals a pause, the semicolon more of a pause. A colon functions as a kind of California rolling stop, and the period commands a full stop. It is a writer’s prerogative to step on the gas or hit the brakes.

We must think upon the comma. Last year The Washington Post carried a lead editorial on a tax bill. It began: “Congress is preparing an overhaul of corporate taxation that could inflict further complications on the tax code, confirm the belief of corporations that ruthless lobbying pays off handsomely and drain more than $150 billion from federal revenue over 10 years.”

Try your hand at copyediting. Would you have inserted a lower squiggle after “handsomely”? I believe a comma would have helped to separate the direct objects of the three verbs in the “that” clause. The same useful purpose could have been served in a more cumbersome fashion by resorting to parenthetical numeration, e.g., “… an overhaul that could (1) inflict, (2) confirm, and (3) drain.”

The upper squiggle also tests a writer’s judgment. During the Democratic convention of 2004, The New York Times reported “the possibility of Kerry attending the final Yankees-Red Sox game.” In this construction, “attending” functions as a gerund, i.e., a verbal noun. Most writers would agree that the noun belongs to Kerry. As such, it required a possessive apostrophe. At least I believe it did, thus, “Kerry’s attending” the game.

The point is arguable. How would you handle, “I can’t imagine Kennedy voting to confirm Roberts”? Would you emend it to read, “Kennedy’s voting to confirm Roberts”? One is reminded of Lyndon Johnson’s days as a novice teacher applying for a job in the fever swamps of Texas. Asked about the Earth, he said he could teach it round, or he could teach it flat.

Would you have put a comma after “round” in the foregoing sentence? I just did, because I tried the sentence both with a comma and without a comma, and “with” was better. I felt the sentence really needed one.

James Kilpatrick is a syndicated columnist.