This is the first edition to provide the complete text of both the fifth-century Calculus of Victorius of Aquitaine and Abbo of Fleury's Commentary on it (written 980/5). These two works are witnesses to an intriguing stage of the history of mathematics, before the introduction of Arabic numerals, when calculations were often quite complex. The wide range of Abbo's thought is reflected in the Commentary, covering the nature of wisdom, the philosophy of number, the relationship of unity and plurality, and the arithmetic of the Calculus. Abbo drew on his knowledge of grammar, logic and cosmology to illustrate his arguments, and set it all in the broader context of his theology of Creation. This edition (which includes an English summary of the text) is crucial for our current reappraisal of Abbo of Fleury as a major figure of the tenth century, who had a profound impact on later medieval English thought. | 
