This discourse wasn’t anything particularly special. Anselm was a medieval monk in France who later became the Archbishop of Canterburry, back before the Church of England “adopted” Canterburry Cathedral and Diocese. The text is an interesting attempt to prove the logical necessity of the existence of God… even the logical existence of the trinity. I’m not a swift-footed enough logician to find where flaws I feel certain there must be in his argument, but I’m glad to have experienced this important part of Christian history.
Anselm attempts to do more briefly and concisely in the Proslogion that which he did in the Monologion, prove the logical necessity of the existence of God. He develops what has become known as “the ontological argument for the existence of God.”
Man understands that something exists greater than which cannot be thought. But anything thought would be greater if it existed both in thought and in reality. So, that than which a greater cannot be thought must exist in reality or it is not actually that than which a greater cannot be thought. And, you guessed it, God is that than which a greater cannot be thought.
Gaunilo was a fellow Benedictine monk, though no philosopher, who sought to show that philosophy and religion are poor bed fellows. He tries to disprove Anselm’s argument, not because he thinks God doesn’t exist, but because he is skeptical of Anselm’s idea, adopted from Augustine, of faith seeking understanding.