whereby intelligibles are comprehended through intermediaries, and perceptibles are comprehended through direct observation. It serves as a likeness (mithāl) to both this world and the Hereafter."

The Brethren of Purity (Ikhwan al-Safa):

"The Intellect is a simple, spiritual substance, simpler than the Soul and more noble than it, capable of receiving perpetuity from the Creator, the Exalted. The proof that the Intellect is more noble than the substance of the Soul is manifest and apparent to every rational person; namely, that since man is superior to all other animals beneath the celestial sphere of the Moon, and his superiority is derived solely from his intellect and not from the perspective of the soul—inasmuch as all other animals possess souls—this suffices as evidence that the Intellect is more noble than the Soul.

As for the Soul (al-Nafs), it is a spiritual substance, knowing potentially ('allāmah bi-al-quwwah), active by nature, receptive to the virtues of the Intellect without the constraint of time, and active within Primary Matter by imparting motion to it across time.