R. G. Latham, A Handbook of the English Language
“ Now if the relation alone between two words constitute a case, the words a child, to a father, of a father, and father's, are all equally cases; of which one may be called the accusative, another the dative, a third the genitive, and so on.Perhaps, however, the relationship alone does not constitute a case. Perhaps there is a necessity of either the addition of a preposition (as in of a father) , or of a change in form (as in father's) . In this case (although child be not so) father's, of a father, and to a father, are all equally cases. ”
