Things Are Known Through Their Opposites

It is evident that the doctrine of divine unity implies predestination. Where God is and naught beside Him, there can be no other agent than He, no act but His. "Thou didst not throw, when thou threwest, but God threw" (Kor. 8.17). Compulsion is felt only by those who do not love. To know God is to love Him; and the Gnostic may answer, like the dervish who was asked how he fared:
"I fare as one by whose majestic will
The world revolves, floods rise and rivers flow,
Stars in their courses move; yea, death and life
Hang on his nod and fly to the ends of earth,
His ministers of mourning or of joy."

This is the Truth; but for the benefit of such as cannot bear it, Jalaluddin vindicates the justice of God by asserting that men have the power to choose how they will act, although their freedom is subordinate to the divine will. Approaching the question, "Why does God ordain and create evil?" he points out that things are known through their opposites, and that the existence of evil is necessary for the manifestation of good.
"Not-being and defect, wherever seen,
Are mirrors of the beauty of all that is.
The bone-setter, where should he try his skill
But on the patient lying with broken leg?
Were no base copper in the crucible, H
ow could the alchemist his craft display?"

R. A. Nicholson - The Mystics Of Islam