A critical evaluation of the relation between mathematics and truth in Alai̇n Badi̇ou's philosophy of being

Looking at the ontological approaches toward the most essential question in the intellectual history, i.e. "what is, what is not?" we observe several philosophers' attempts to enlighten "one and many question" since pharmenides' times. in this context main topic of this dissertation is the ontological approach of alan badiou, a distinguished philosopher of modern philosophy, who defends that many overcomes one in the existential field. particularly these two issues are examined here: what badiou means by the statement "mathematics=onthology" and how he established generic thought system with the development of set theory -transcendental and constructive- thinking orientations that he groups under two categories. Besides it is also elaborated how generic thinking orientation carries subject to an effective point on the way to become the creator of the truth. Keywords: Philosophy, Mathematics, Ontology, Set Theory, Badiou, Model Theory, Subject Theory.