  Albert was interested in certain mathematical problems. To this end, he wrote a question on the squaring of the circle as well as questions on John of Sacrobosco’s Treatise on the Sphere. In addition to authoritative arguments and purely empirical justifications, his question on the squaring of the circle uses properly mathematical arguments appealing to both Euclid (in the version of Campanus of Novarra) and Archimedes (translated by Gerard of Cremona). His most original contribution is a proposal to dispense with Euclid’s proposition X.1, replacing it with a postulate stating that if A is less than B, then there exists a quantity C such that A&lt;C&lt;B.