Today on the Mental Floss blog there was a post that dealt with many common grammar questions. I particularly found this interesting, because it addressed a pet peeve issue of grammar for me. Allow me to save you the time of visiting the site by just copying it below.
Q: “I feel like I remember having read in my old college Chicago Manual of Style that there are a select few proper names for which the possessive is ’ and not ’s. I think one was Jesus (as in ‘He followed Jesus’ teachings,’ not ‘He followed Jesus’s teachings’). I think it was the same for Moses and Sophocles … am I making this up?”—Posted by lala on 5/8
A: You remember correctly! The usual practice in making names possessive is to add an apostrophe plus s. But there’s an exception. When a Biblical or classical name ends in s, the custom is to add just the apostrophe: Jesus’ disciples, Hercules’ strength, Xerxes’ writings, Archimedes’ principle.
We also drop the s and use only the apostrophe in certain idiomatic expressions with the word “sake” (this avoids a pileup of sibilants). Examples: “for goodness’ sake,” “for conscience’ sake,” “for righteousness’ sake,” “for convenience’ sake.”
The strange thing is I’m horrible at grammar. I do believe I have some struggles with dyslexia, which I’ve learned to combat by quickly viewing a sentence and never really noticing what I actually read. I have to focus on the bigger idea more than the small details otherwise I get lost. So I can not say that I’m perfect in all areas of grammar, but when people verbalize this above mistake it grinds my gears. I even heard the king of Christian literature, Max Lucado, say “Jesus’s” before.
Anyways I post this because when I complain about it and people ask for the grammatical rule I’m not qualified enough to give a good answer. Hopefully this helps.
If you have other grammar questions you can visit the grammarphobia site.