In this study we took in hand Aristotle and Plotinus’ “The One” philosophy in the notion of “The One" perspective and we tried to determine its place in ibn Sina’s thought. In this study we took in hand the approach in three perspectives in the unity of the essence of the existence numerical one, obligatory ones unity; first principle, the one, and the compulsory being. The ontologic and epistemologic meaning of the concept one’s foundations, its structure and meaning, its indivisibility in Ibn Sina were determined by Aristotle. In the compulsory unity, on the other hand, together with Aristotle Plotinus’s philosophy consists the base of the Ibn Sina philosophy