William Lane Craig a well-known philosopher and Christian theologian, as well as a historian and apologist. A professor at Talbot School of Theology and Houston Baptist University, Craig is perhaps best known for defending the Kalam cosmological argument, and for debates that are available on YouTube. Craig’s website is Reasonable Faith.
In this video from Reasonable Faith, Anselm's Ontological Argument is presented. Anselm of Canterbury wrote that God is "that than which nothing greater can be conceived", and believed that if it's possible that a 'maximally great' being exists, then that being must exist. See what you think.