Abstract
Reflecting on Avicenna’s works indicates that by ‘Dhat’(ذات), when used in the context of universal essences, he means either the quiddity or the nature, and when used in the context of individual essence, especially God’s essence, he means the very existence. The second meaning, i.e. the nature, which is the result of his inquiry about the reality of things, is based on the first one, i.e. the quiddity. According to this second meaning, and througha kind of thought experiment and using human mind’s capacity, Avicenna discusses different aspects of essence and their implications in various sciences. These conceptual analyses help us discover his idea of essentialism. The final conclusion is that Avicenna’s essentialism is consistent with his idea about existence and the definitions can refer to the essence of objects.