Socrates' OR Socrates's

[atabitaraf]

After viewing 3 books: 1. Digest, 2. English grammar in use, and 3. Practical English usage, on possessive apostrophe, in just one book, the last reference, it is written: for older and foreign names ending in s we can use either 's or '. However it claims that using 's is more common.
To be sure I ask you if it is correct to say
1. Socrates' ideas
OR
2. Socrates's ideas

 

[MikeNewYork]

Both methods are used. I believe that the 's method is more common.

 

[atabitaraf]

As a matter of fact, my practical rule is: We use 's except when the word is a plural noun ending in s.

John's car.
Chris's car.
My parents' car.
My boss's car.

Is it correct?

 

[tedmc]

The apostophe 's' is used and is pronounced 'Socrateses', like the possessive used after names ending with 's', e.g. Jameses, Rosses, Thomases, etc

 

[MikeNewYork]

As a matter of fact, my practical rule is: We use 's except when the word is a plural noun ending in s.

John's car.
Chris's car.
My parents' car.
My boss's car.

Is it correct?

That is a pretty good practical rule.