Avicenna

Avicenna, a Persian philosopher, explored fundamental concepts like "substance" and "essence." Substance refers to what something fundamentally is—its core existence, while essence describes what defines a thing’s nature or qualities. For instance, the substance of a cat is "cat-ness," while its essence includes traits like being furry or a hunter. Avicenna argued that understanding these concepts helps us grasp the nature of reality, including the existence of God. He emphasized that true knowledge comes from distinguishing between what something is (its essence) and its independent existence (its substance).