 Natural powers are obviously nobler than artificial ones. Avempace also takes modal factors into account for his design and introduces necessity in his discourse. Necessity is predicated of immovable forms in its primary sense, and metaphysics deals with them. The natural scientist deals with forms subject to motion and, for this reason, necessity can be predicated “by design” bi-l-wad‛. Avempace gives the following example that clarifies what he means with “by design”: