Why is it “ich” and not “mich” in the sentence “Er war kleiner als ich”?

Question

Every time I think I understand accusative, I find something that pokes holes in my understanding. Most recently, I’ve operated on the understanding that any time you have two distinct entities (e.g., in _Ich habe einen Bruder_) one of them must be accusative (in this case, _Bruder_ which we see in the _-en_ addition to the indefinite article). This does not apply to _Er war kleiner als ich_, though, and I’m not sure why? I wrote the “incorrect” version in an edit (_Er war kleiner als mich_), and someone very reputable corrected it as _ich_.

Answer 1

The above sentence "er war kleiner als ich" is a comparison, you will find that both parts of comparisons will take the same case in German. Moreover, you are using the verb "to be" in this comparison (very common for comparisons). This means that the two nouns being compared are both the subject and therefore in the Nominative case.

Other examples:

Meine Schwester ist schlauer als mein Bruder.

Ich bin kleiner als du.

Seine Frau ist nicht so schön wie meine Frau.

However, the other cases are also possible in comparisons. Again, both parts will take the same case:

Mein Hund mag dich lieber als mich. (both Akkusative)

Unsere Eltern geben dir mehr Schokolade als mir. (both Dative)

Your sentence "Ich habe einen Bruder" does not follow this pattern and the accusative is needed because of the verb "haben" (full verb). Your "rule" of having two entities, therefore one of them must be accusative will likely be confusing in sentences like: "Sie schenkt ihm ein Buch" and will not help you in sentences like "Ich helfe dir gern".

Hope this helped.

Ursula