وثانيها: مباديه، والمبادي ما يبتني عليه المسائل
The second element is a science's principles: matters on which its issues depend.
Principles are not simply preliminary vocabulary. They are concepts or premises necessary to formulate or demonstrate the questions studied by a discipline.
For example, a proof by syllogism presupposes understanding “middle term,” “minor premise,” and “major premise,” and it must also rely on appropriate propositions. These different dependencies point to two classes of principles.