Given the beliefs of Abrahamic religions, God is the ultimate reality, he is absolute needless from others while all other are absolutely dependent on him. On the other hand, there are truths which are absolutely necessary and are true in any circumstances. If there are absolutely necessary truths that are independent of their truth, then there will be a scope of reality that is independent of God; and therefore God is not the sole ultimate reality.

In order to resolve this controversy, the theists should explain the origin of God to these truths. By focusing on the necessary truths specific to the creatures - especially the truth of possibility – Brian Leftow carry out the question: what is the ontological basis for necessity of creatures’ possibility. Before we ask: "Why is there human being?" we should ask, "Why is human being possible to being?"

Most theist's response to this issue by using nonvoluntaristic approach (called Deity theories by Leftow) believe that the assumption of the essence of God implies the truths of possibilities. On the other hand, some of the theists using voluntaristic approach, believe that just being of divine nature does not entail the realization of the truths of the possibilities, but must be something related to a factor of the will.

Brian Leftow, by criticizing Deity theories, has chosen the moderate voluntaristic approach, according to which being of nature is not enough solely and the factor of will and power are important. We have found that Leftow's critique of deity theories and his voluntaristic approach is incompatible with his basic assumption, the divine ultimacy doctrine, and at least some of deity theories are more consistent with this doctrine.

Keywords: Voluntarism, Divine Ultimacy, Necessary Truths, Modal Metaphysics, Necessity, Possibility, Perfect Being Theology, Brian Leftow.