Kasus & Präpositionen

Casus and Prepositions

In this post we learn further that verbs are not the only ones that determine what case a noun takes as a complement in a sentence. Prepositions also do depending on the verbs used in a sentence. There are nine such prepositions known as dual prepositions (Wechselpräpositionen). 

German language has some prepositions which are fixed (feste Präpositionen in German) and always govern either the accusative (bis, durch, für, gegen, ohne, um) or the dative (aus, außer, bei, mit, nach,  seit, von, zu) and nine dual prepositions (Wechselpräpositionen) which form sentences with either the accusative or dative case.   

These dual prepositions are: an, auf, hinter, neben, in, über, unter, vor, zwischen.

These nine prepositions normally form a sentence with accusative when used with transitive verbs such as legen, setzen, stellen, whos nature and meaning require that they are complemented with a double accusative in a sentence with the question wohin?

Der Lehrer legt den Stift auf den Tisch (Wohin legt der Lehrer den Stift?)  Wohin?+Akkusativ

The very same prepositions form a sentence with a dative when used with intransitive verbs such as liegen, sitzen, stehen with the question wo?

Der Stift liegt auf dem Tisch (Wo liegt der Stift?) Wo?+Dativ

PS: 
The majority of German verbs are transitive. These types of verbs will always take the accusative case when used in a sentence. This means that the verb needs to be complemented with an accusative object in order to make sense.

If you want to convey a direction or destination in a sentence, then you need to use the accusative. These sentences will always answer the question where to (wohin?)

The dative case is used to indicate a stable position or situation. It answers the question where (wo?)

Intransitive verbs do not take a direct object and will always take the dative or genitive case when used in a sentence. Although the verb gehen (to go) is intransitive it is an exception to this rule. Since the subject here is moving from point A to point B the accusative will have to apply in order to indicate the movement of the subject (wohin?) same way we indicate the movement of the object by the subject from point A to point B with transitive verbs.

Examples:  

Er geht in den Supermarkt.

Wir gehen in die Kirche(church).

Geht ihr ins/in das Restaurant?