Text 12. When Tûsî finished investigating the five categories which inhere in the ten categories, he began the investigation of [the ten], even though [such investigation] is not part of logic. [This is] because the subject matter of logic is the secondary intelligibles which inhere in the primary intelligibles. How can the primary intelligibles be investigated even though [such investigation] is a [presupposed] part of the science [of logic]? This would be circular. But rather, [the ten categories] are investigated in logic to aid in properly realizing the genera and specific differences. [Such investigation], then, will be a help in discovering (istinbât) what is defined and inferred, even though it is not part of logic (Hillî Jawhar [1410 A.H.]  23.4–8).