Anselm of Canterbury, Saint. Article #16. Vol 1, pg 434.
Anselm of Canterbury (1033-1109) was born in Italy, but found his way to France, where he eventually became the abbot of the monastery of Bec. He later became Archbishop of Canterbury, in 1093, but he butted heads with King William II over whether it should be William II or the pope who should invest Anselm with the symbols of his office.
Anselm is best known for coming up with the ontological argument for the existence of God, which goes something like this. Being imperfect beings, we can all imagine the most perfect being in the universe (i.e. God). Furthermore, this being must exist, based on the fact that the idea exists.
Critics of Anselm weren’t buying it. Just imagining that something exists doesn’t prove that the thing actually exists, they said.
“Anselm of Canterbury, Saint.” Encyclopedia Britannica. 15th ed. 2010. Vol 1, pg 434.