Many theists use a cumulative case approach to argue for the existence of God. They appeal to several theistic arguments including the ontological argument, the cosmological argument, the contingency argument, the fine tuning argument, the moral argument, the reformed epistemological argument, etc. These are valid theistic arguments that can be used to present good reasons to believe that God exists. With a cumulative approach, I think we can argue by ‘inference to the best explanation’ that the existence of God is the most powerful explanatory story of the universe, humanity, morality and eschatology. However, because I use a narrative theological method, I prefer Anselm’s ontological argument for the existence of God, which I find conducive to storytelling.
The ontological argument is a metaphysical argument that emphasizes the nature of “being” (gr. ὄντος, ontos) and draws upon logic rather than empiricism. Thus, the ontological argument appeals to “a being that which nothing greater can be conceived,” and that this being “exists both in the understanding and in reality.” The deductive argument posits that things can exist in understanding alone or in both understanding and reality, but that to exist in reality is greater than to exist in understanding only; thus, if a being only existed in understanding, then it would not be the greatest possible being “since a being that existed in reality would be greater.” The ontological argument follows Anselm’s line of thinking regarding the existence of the greatest possible being and concludes that this being is God, and so God exists. Another feature of Anselm’s thought is that God’s existence is a “necessary existence” or “a matter of logical necessity.” He wrote, “God cannot be conceived not to exist. God is that, which nothing greater can be conceived. That which can be conceived not to exist is not God.”
With the help of this argument, I prefer speaking ontologically that God is the greatest being, and then I prefer to transition into speaking narratively about the Theo-drama of redemption that culminates in the life and ministry of Jesus, which then enables me to appeal to an evidential apologetic approach that presents the historicity of Jesus’ life, death, resurrection, and ascension.
I think that a progression from the ontological argument to the Theo-drama to the evidences of Jesus’ redemptive life and ministry gives a strong unified, explanatory argument for the existence of the Judeo-Christian God. This is the story that Christians have told throughout the centuries. That there is an ultimate being who many have appealed to as “an unknown God,” (Acts 17) but this greatest being has acted and revealed himself in the Theo-drama of redemption throughout the storied history of Israel and the Church. Christians proclaim the eyewitness stories of Jesus’ redemptive life, death, resurrection and ascension, and they tell the future eschatological story of the return of King Jesus, who will establish his eternal kingdom.
 Anselm Proslogium 2, in Internet Medieval Soursebook <www.fordham.edu/halsall/basis/ anselm-proslogium.html#CHAPTER%20II> quoted by Douglas R. Groothuis, Christian Apologetics : A Comprehensive Case for Biblical (Downers Grove, IL: IVP Academic, 2011), 187.  Anselm, Proslogium, 2 quoted by Groothuis, Christian, 188.  Groothuis, Christian, 188.  Groothuis, Christian, 195.  Anselm, Proslogium, 2 quoted by Groothuis, Christian, 194.