On the Interior Senses
Latin Grammar: Partitives: Genitive and Ablative
Sed virium ab intus apprehendentium, quaedam apprehendunt formas sensibiles, quaedam vero apprehendunt intentiones sensibilium. Apprehendentium autem quaedam sunt quae apprehendunt et operantur simul, quaedam vero apprehendunt et non operantur, quaedam vero apprehendunt principaliter et quaedam secundario.
The genitive is commonly used in a partitive sense; that is, focusing on some part of a whole, as quaedam virium, "some of the faculties." Another way to express partitives is with the ablative: quaedam de multis, "some of many." When do we use the genitive and when do we use the ablative? The ablative (with the preposition e (ex) or (de) is used most of the time with cardinal numerals (duo ex viribus), and some of the time with quantitative adjectives like unuspauci. While the rules are not hard and fast, a good rule of thumb is that when the focus is on enumeration, the ablative is used, and otherwise the genitive is used.
Exercise: Use the guidelines above to translate the English partitives below into Latin.