Use of article instead of possessive: "die" vs "seine"?

Question

I've been working on my German recently by reading through a book, originally in English, translated into German, and I keep coming across some phrasings that look very strange to me.

For instance, this one:

Er streckte die Hand aus.

Shouldn't that be this?

Er streckte seine Hand aus.

Then, a couple lines later, again:

Er ließ die Arme an seine Seiten fallen.

I'm a little confused at the use of die instead of seine. In fact, I'm finding a lot of the usage of particles and pronouns very confusing.

Can someone explain why die is the correct word here? I'm sorry if this is something really simple, but I don't understand the rule for when it is appropriate to use the possessive pronoun as opposed to the article.

Answer 1

German absolutely permits both forms (article or pronoun) - unlike English, for example, where you would always expect a posessive pronoun. I'd suppose the original of your book would be "extended his hand".

It's mostly a question of literary style, which one is choosen if the context permits.

But: The context (oh how we love this word here!) should be still unambiguous if only the article instead of the posessive pronoun is used, otherwise clarify via the pronoun.
An example:

Der Mann zog die Frau aus dem Wasser und legte sie ans Ufer. Dann hob er die Arme und...
a_1)...rief die anderen Retter herbei. (-> his arms, presumably) or
b_1)...legte sie neben ihren Körper. Er weinte bitterlich. (-> his? hers? works both... one implies bending down over the victim in grief, one straightening out her body.) or
c_1)...legte sie neben ihren Körper, damit sie ihm bei der Ersten Hilfe nicht im Weg waren. (-> her arms)

Much clearer would be using the appropriate pronoun right away, making only one option possible:

Der Mann zog die Frau aus dem Wasser und legte sie ans Ufer.
a_2) Dann hob er seine Arme und rief die anderen Retter herbei. or
b_2) Dann hob er seine (or ihre) Arme und legte sie neben ihren Körper. or
c_2) Dann hob er ihre Arme und legte sie neben ihren Körper.

Another rule of thumb when using the article instead of a pronoun:
We humans expect continuity, in this case, we expect "the owner" to be the subject of the sentence (this is why example a_1 feels more "smooth" that c_1 and we tend to understand "his" in b_1) unless context says otherwise.

Answer 2

You should use the possessive pronoun to avoid confusion. If, for example, it was unclear whose arms he dropped. This is not the case, so you can use the article. In the second example, it is also more elegant than using the (same) possessive pronoun twice in the same sentence.

Answer 3

Er streckte die Arme aus.

Unless we are talking about somebody else's arms, it's clear that they are his, so there's no need for the possessive pronoun in German. It's certainly not wrong, though:

Er streckte seine Arme aus.