To s, or not to s, that is the question

Happy New Year!

This year I want to concentrate in the blog on the Big Issues, the issues that grab you by the balls (if you're male) and kick you in the guts (unisex) with their desperate relevance to our lives. So let's begin with possessive apostrophes.

If you think this isn't important, then clearly you don't write Greek or Egyptian historicals. The Greeks had a love of names ending in -s. Nicolaos, Socrates, Pericles, Sophroniscus, Callias, Themistocles...at least half the names I need.

I was taught in school that a proper noun ending in -s has a possessive with only the apostrophe and no following s. So:

Pericles' scroll

Which is exactly what I have done throughout two novels, and when half your characters have names ending in -s, that's an awful lot of trailing apostrophes.

So far so good, except the style elsewhere appears to be quite different. To pick a random example:

Thutmosis's slingshot

Stephen King, in his essay On Writing, says the 's goes on the end of every proper noun no matter what.

The Chicago Manual of Style, which I have never read, apparently straddles the barbed wire fence by saying King got it right but that my convention is an acceptable alternative.

My OED gives clear examples my way, such as Apostles' Creed, but any search of printed books produces examples always using 's. So at this point I'm wondering if it's a UK vs US difference, except a net search finds plenty of Americans as confused as I now am.

It might help knowing English belongs to the Germanic family of languages, and -es is the most common of several possessive endings in German. Our possessive is precisely the German neuter version, but with the e of -es excised and the apostrophe showing where it used to be. Would it make sense in German to end only with the e? No. By that logic, King is right and it should always be 's. Except English parted ways with German some time ago.

One thing's for sure. If Stephen King is right, then my copyeditor at St Martin's is having a nervous breakdown.