Possible Duplicate:
When should I use “each other” vs. “one another”?
It occurred to me recently that I've been using these phrases interchangeably (basing my decision purely on how formal I want to sound). Are they really interchangeable?
What's the appropriate usage in:
"Human beings often fail to understand what's most important to [___]..."
Is it "one another", "each other", either, or neither?
The standard rule is:
Use "each other" to refer to two entities that are exchanging something.
Prefer "one another" when there are three or more in question.
Neither usage is appropriate. Without context, I have no idea what this "most important" thing is (perhaps, as the statement implies, simply because I'm a human being).
It would be perfectly reasonable to end the sentence at the word "important". Semantically (but not stylistically) it could reasonably end with "to human beings" as far as I'm concerned, but someone else might say it should end with "to God's plan", "to world peace" or just about anything the writer thinks is important, but which he thinks others don't "get".
EDIT: Thanks to @RegDwight for pointing out an obvious interpretation of what's most important that I simply failed to spot. If what a person (i.e. - people in general) fails to understand is what's important to another person or to other people, the form should be...
Human beings often fail to understand what's most important to others.
