ones - Plural von "one"
one's - Genitiv von "one"

wie soll das näher bestimmt werden?

Na, im Hinblick auf syntaktische Funktion oder Wortart. Der Unterschied Genitiv - Plural ist mir natürlich klar, aber ich würde eben sagen, dass es sich im angegebenen Beispiel 1 um einen Artikel (oder allg. Determiner), in Beispiel 2 aber um ein Pronomen handelt. Dessen bin ich mir aber nicht hundertprozentig sicher.

They are both pronouns.

http://dictionary.cambridge.org/results.asp?s...
http://www.chambersharrap.co.uk/chambers/feat...

Vielen Dank - wobei ich mir einfach nicht genau sicher bin, welchen Fällen die Beispiele entsprechen. Ist mir zwar etwas peinlich, aber irgendwie bin ich - vielleicht erkältungsmäßig - gerade auf den Kopf gefallen. :-/

pronoun 1 (often referring to a noun already mentioned or implied) an individual person, thing or instance • buy the blue one. 2 anybody • One can't do better than that. 3 formal or facetious I; me • One doesn't like to pry.

One favours a model that agrees with one's fundamental beliefs.
= 2 or 3
I bought four nice ones
= 1

I don't know enough about grammar to be able to tell you specific names for these two forms apart from "pronoun", sorry.

Ups, that was my fault then. In the first case, I'd like to know the status of the second 'one': "... that agrees with one's fundamental beliefs." Still a pronoun in your opinion?

But thanks for the help with the other one, I certainly agree with you!

It favours a model that agrees with its fundamental beliefs.
One favours a model that agrees with one's fundamental beliefs.

I see what you mean. You're right: "one's" is a determiner, like "its": http://dictionary.cambridge.org/define.asp?ke...

The blue ones are delicious - pronoun
That depends on one's point of view - possessive pronoun [like his, her, your, their, etc.]

That depends on one's point of view

Sorry, it seems like the more proper term for these words is "possessive adjective". However, there seems to be some disagreement and variation on what exactly is the proper term for these words.
http://en.wikipedia.org/wiki/Possessive_adjec...

Many thanks for all your thoughts and suggestions. Indeed, I have already heard the term "possessive adjective" - and found a grammar book that makes reference to this term, too :-)
Howard Jackson, Analyzing English (1985 [1980]: 64)

That depends on one's point of view.
--> one's = "possessive adjective" aka "determiner"!

I disagree with the conclusion in #10.

First of all, it is indeed important to distinguish between determiners and pronouns. Determiners function like adjectives, pronouns function like nouns.

Example: "my" is determiner (possessive adjective), "mine" is pronoun.

"One" is a pronoun, i.e. functions like a noun. This does not change when we put the pronoun into the possessive case.
"That depends on one's point of view." is the same construction as
"That depends on Peter's point of view.", i.e. "one" functions like a noun and therefore is a pronoun here.

#11 That is just looking at "one", though, not "one's". If "my" or "its" can be a determiner (see above), can't "one's" be one too? I brush my hair, one brushes one's hair. Why is "my" a determiner, but "one's" a pronoun plus genitive?

Hmmm, I'm not sure what you mean, Londoner, but I would say in your example sentence "Peter's" functions as an adjective (which is one type of determiner). It describes the "point of view". The fact that it is derived from the name Peter doesn't change anything. Context determines function.
The outrageous, ridiculous, old-fashioned, my, her, the gentleman's, Peter's, one's point of view. They are all just different types of adjectives or determiners. Some possessive adjectives get by showing possession without the use of an apostrophe, others need one.

"That depends on one's point of view." is the same construction as
"That depends on Peter's point of view.", i.e. "one" functions like a noun and therefore is a pronoun here.

Yes, "one" functions like a noun, but the word in question here is "one's", not "one".
"She" is a pronoun, but "her" is a possessive adjective. Similarly, one is a pronoun and one's is the corresponding possessive adjective. You can't use these words as nouns, so they can't be considered pronouns. That's how I see it.

re #11, #12:

1. Just to make a short point: have you ever seen an adjective in the English language that can have a possessive case?
Only nouns have a possessive case (in English), and as "one's" clearly is in the possessive case (how would you explain the "'s" otherwise?), it must be fulfilling the function of a noun, and not of an adjective. Therefore, "one's" is a pronoun.

2. Another line of argument: If "one's" were a determiner, one would expect that "one" could be used as a determiner, too. Obviously, it can't. How do you explain this discrepancy?

In sum, wha do you gain by classifying "one's" as a determiner? In contrast to this, classifying it as a pronoun has a clear explanatory value.

@wupper: It does not make sense to compare "she" and "her" with "one" and "one's". The counterpart to "one's" would be the possessive case of the personal pronoun "she", which is "hers".

Sorry, my comment in #14 is meant to refer to #12 and #13, of course.

@ CM2DD: Same thing as my comment on wupper: The couterpart of "one's" is "mine" and "its", not "my" and "its".

This topic shows very well why it makes sense to distinguish clearly between pronouns and determiners.

a) Personal pronouns
Subject case: I, you, he, she, it, we, you, they
Object case: me, you, him, her, it, us, you, them
Possessive case: mine, yours, his, hers, its, ours, yours, theirs

b) Possessive determiners
my, your, his, her, its, our, your, their

In this context, "one" is another personal pronoun with the subject case "one", the object case "one" and the possessive case "one's". Since there is no specific possessive determiner for "one" (as there is no specific possessive determiner for "Peter" either), we use the possessive case of "one" to mark possession. (Wenn man das Deutsche "man" als Gegenstueck sehen will: dort wird ersatzweise der possessive determiner der dritten Person Sg. neutrum verwendet.)