Combinations of nouns with prepositions in certain object and attributive collocations are understood as morphological case forms. So there are distinguished:
1) the ‘dative’ case: (to + Noun, for + Noun)
2) the ‘genitive’ case (of + Noun).
These ‘prepositional cases’ coexist with positional cases and the classical inflexional genitive of the English noun.
The blunder of this theory: it is well known from noun-declensional languages, all their prepositions require definite cases of nouns (prepositional case-government); then it should follow from this that not only the of-, to-, and for-phrases, but also all the other prepositional phrases in English must be regarded as ‘analytical cases’ which leads to illogical redundancy ‘prepositional cases’.