This study offers an interpretation of the argument of the Proslogion as an epitome of Anselm's world of thought. The main part of the book is concerned with the unum argumentum, which constitutes the whole text of the Proslogion. Interpreted as a search for the origin and limit of thought, the argument cannot be understood as an "ontological proof" for the existence of God. Next, the author shows the ways in which Anselm has been misperceived and "mystified" by subsequent interpreters, and argues that the Proslogion must be understood as an element of Anselm's practice of wisdom.