不好意思，想請問Genitive與ablative of Description兩者之間的差別？
什麼時候用前者，什麼時候用後者？
A Primer of Ecclesiastical Latin上的例子：
1.Genitive
Sumus populus misericordiae?
Primi Christiani erant homines laeti animi.
2.Ablative
Petrus erat vir magna anima.
Gratia.

Ablative Description, especally of physical qualitiesGenitive Descri, especally of Non-physical qualities以上，來自Cambridge Latin Grammar, page53, 50