Now, apparently I was wrong, too, or at least, not quite right. A scholar has found several similar prayers that were actually published prior to the "official" publication date of Niebuhr's Serenity Prayer in 1943. The various candidates:
The original, canonical form attributed to Niebuhr in 1943: "God grant me the serenity to accept the things that I cannot change; courage to change the things I can; and wisdom to know the difference."
A prayer by Miss Mildred Pinkerton printed in the Syracuse Herald, January 16, 1936: "O God, give us courage to change what must be altered, serenity to accept what cannot be helped, and insight to know the one from the other."
A prayer by Miss Constance Leigh, from the Hartford Courant, October 27, 1938: "I would in closing this brief report voice the hope that we may have the courage to change what should be altered, an understanding and serenity to face what cannot be changed, and the wisdom to recognize one from the other."
I get the point of the critics, but I don't know whether this changes anything. Niebuhr can still be credited with the particular linguistic formation that we canonically understand as the Serenity Prayer. Neither of the two "originals" are the same as the Serenity Prayer that many today recognize. In fact, while they share a similar structure, they lack the simplicity, grace, and power of Niebuhr's particular formulation. In this regard, we can say that Niebuhr indeed "authored" the prayer, in the same way that Henry Ford "invented" the assembly line, even though he incorporated the techniques from meat packing plants.
“Reinhold Niebuhr was a very honest person who was very forthright and modest about his role in the Serenity Prayer," said Fred R. Shapiro, the Yale librarian who found the two earlier versons. "My interpretation would be that he probably unconsciously adapted it from something that he had heard or read.”
Niebuhr may have borrowed the basic sentiment behind the other two prayers—though we would have to establish that he knew these prayers to determine whether he was truly inspired by them—or his prayer may simply reflect the intellectual and spiritual climate of American mainline Protestantism during the Depression and Second World War. (The latter may be more accurate.) But we shouldn't be surprised by this. There is no such thing as a "new idea," only old ideas that are used and reformulated to meet the needs of a particular time. This is what Niebuhr was doing, and we still do the same today.