The tribulations of Delaware's Sen. Joe Biden bring to mind an occasion of personal pain. The first of several charges that forced the gentleman out of the presidential race was that he had engaged in plagiarism. Among other things, he had borrowed some good lines from other politicians, and he had paid no interest on the loans. The incidents appeared to be patent plagiarism, and that was the beginning of Biden's end.

Let me make a confession. It is a confession I have made publicly before, but the Biden story gives it fresh currency. I too have committed plagiarism.

It happened in this fashion. Three or four years ago -- I forget when -- I wrote a column that touched lightly upon the German language. I cannot find the column, but I said something to this effect -- that when a German dives into a sentence, that is the last you will see of him until he emerges at the end of his sentence with the verb in his teeth. Cross my heart, when I wrote that line I honestly and truly believed it to be my very own.

You may therefore understand my shock, chagrin, embarrassment and horror when a gentlewoman in New England wrote me a reproachful letter. She pointed out that in ''A Connecticut Yankee in King Arthur's Court,'' Mark Twain had preceded me. Twain had written:

''When the literary German dives into a sentence, that is the last you are going to see of him until he emerges on the other side of his Atlantic with his verb in his mouth.''

I was struck dumb -- and for good reason: I had never in my life read ''A Connecticut Yankee in King Arthur's Court.'' To this day I have not read it. The work is not in my library. Yet any jury in the world, comparing the two passages, would find me guilty of grand larceny. I would have apologized to Twain, but he was long since dead. My only recourse was to make public confession and to try to put the matter out of mind. A writer never could put such a matter out of mind.

A couple of years passed. Then a gentleman in Seattle wrote me a kindly letter. He recalled a chapter in Twain's autobiography in which Twain himself confessed to an almost identical experience. It is a pity to compress Twain's delightful account of the incident, but let me try.

Twain had published ''The Innocents Abroad'' in 1869. Three years later an old friend put a hard question to him: ''How did you come to steal Oliver Wendell Holmes' dedication and put it in your book?'' Twain couldn't believe it. Alas, it was true. Holmes had published a small book of poems, and there on the dedication page was the precise passage Twain had put forward as his own. He could not remember ever having seen the Holmes book.

Then it came to him. Many years earlier, in Hawaii, Twain had spent two bedridden weeks in a Honolulu hotel recovering from a painful case of saddle boils. He found nothing in his hotel room to read but . . . a little volume of poems by Oliver Wendell Holmes. He read the book to rags, ''without thought or intention of preserving it in memory,'' but somehow the dedication stuck in his mind. He was guilty.

Twain wrote to Holmes and told him ''the whole disgraceful affair.'' He begged for forgiveness and implored him to believe the crime was unintentional. Holmes responded with a letter that Twain cherished.

''In it Doctor Holmes laughed the kindest and healingest laugh over the whole matter . . . and assured me that there was no crime in unconscious plagiarism; that I committed it every day, that he committed it every day, that every man alive on the earth who writes or speaks commits it every day and not merely once or twice but every time he opens his mouth; that all our phrasings are spiritualized shadows cast multitudinously from our readings; that no happy phrase of ours is ever quite original with us; there is nothing of our own in it except some slight change born of our temperament, character, environment, teachings and associations; that this slight change differentiates it from another man's manner of saying it, stamps it with our special style and makes it our own for the time being . . .''

I continue to wonder where I first saw Twain's line about the German sentence. A friend has suggested that perhaps I stumbled over it once in browsing through Bartlett's Quotations, found the line felicitous and tucked it away in a dusty attic of the mind. Perhaps. I would like to believe that I got it from a beautiful German girl at the University of Missouri 50 years ago, but that is another story involving another confession, and prudently I leave it for another day.