The author analyses the place of mathematics and its importance in the thought of Nicholas of Cusa. He understands mathematics as a mirror, where the infinite as the infinite is reflected in the finite. Mathematics is predominantly the science of the visible, and that enables a step-by-step transfer from »the vision of the eye« to »the vision of the mind«. Furthermore, the mathematical entities are the most certain of all the objects of the visible world, and this makes them the most suitable starting point for investigating the uncertain and the unknown. This mathematical certainty is based, according to Cusanus, on the ontological status of the mathematical entities. They are neither suprasensible entities (Plato), nor the principles of t...