The purpose of this article is to reveal al-Ghazali's understanding of God and world on the ontological basis. He bases the purpose of existence of the world with to know God. In such a study, it is difficult to distinguish ontology from epistemology. Al-Ghazali classifies beings in different perspectives. However, all beings consist of the God and acts of God. God is a unique entity, which is compulsory, source of existence and sacred. His adjectives are with him. God is completely different from what he created. Creatures cannot fully grasp it. God is not far from the world, but he is very close to his servants. The world is everything outside of God and his attributes. All beings are acts of God. The world owes its existence and continuation to God. The world that is the act of the God actually introduces us to the God. The purpose of the creation of the world is to introduce God
