Usage concerning “mir/mich”

Question

I saw a sentence in a German textbook:

Aber wenn ich Geburtstag habe, dann darf ich mir ein Essen aussuchen.

I would like to ask why we should use "mir" here? I saw it somewhere else a sentence

Ich darf mich vorstellen

Here "mich" is used instead of "mir". Can someone please explain the differences?

Answer 1

You can translate »mir« as »to me« (in the meaning of »for me«):

Ich suche Essen aus.
I choose food.

The food can be dedicated to me, but also to my neighbor, to my boss, or just anyone. This sentence just says, that i make a decision, but it doesn't say, who is the beneficiary of this decision.

Now with »mir«:

Ich suche mir Essen aus.
I choose food for me.

Now it is clear: The food is dedicated to me. I am the beneficiary of this decision.

You also could say:

Ich suche dir Essen aus.
I choose food for you.

Ich suche meiner Tochter Essen aus.
I choose food for my daughter.

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What is said above has nothing to do with:

Ich stelle mich vor.
I introduce myself.

Ich stelle dich (meinem Chef) vor.
I introduce you (to my boss).

Also compare:

Walter_(nominative) stellt mir_(dative) seine Frau_(accusative) vor.
Walter introduces his wife to me.

Walter_(nominative) stellt mich_(accusative) seiner Frau_(dative) vor.
Walter introduces me to his wife.

Here you tell in dative case who is the person that is introduced (the object of introduction). And in accusative case you tell to whom this person is introduced (the target of the introduction). In nominative case you will find Walter, he is the person who performs the introduction.

In german you define the roles not by position but by grammatical case, which gives German a much greater flexibility in word order than English. So also this sentences are correct sentences (some are unusual, but still correct):

Mir stellt Walter seine Frau vor.
Seine Frau stellt mir Walter vor.
Seine Frau stellt Walter mir vor.
Walter introduces his wife to me.

Mich stellt Walter seiner Frau vor.
Seiner Frau stellt mich Walter vor.
Seiner Frau stellt Walter mich vor.
Walter introduces me to his wife.

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Also note, nothing of what I've said here has to do anything with »darf, muss, kann, ...«

Answer 2

"Ich darf mich vorstellen" parallels the English construction. It means "I must introduce myself," which is "accusative" in both English and German, and therefore uses the "mich" form.

You may be confused because "Ich darf mir ein Essen aussuchen," does not parallel the English construction. The English version would be, "I must seek a dinner," as opposed to "I must seek a dinner for myself."

But Germans are more explicit about recipients, because they might interpret "Ich darf mir ein Essen aussuchen," as "I need to get dinner for someone else."

Hence they add the word "mir" to the sentence, to make it clear that I am getting dinner for myself. And "for myself" is translated using the dative, mir, versus the accusative, mich, when referring only to "myself."