  Zabarella also had to face the question, how the intellect in fact made this mental consideration. He solves the problem in terms of his psychology of knowledge and calls this third step a mental examination (examen mentale). Since for him the task of this intermediary step is to make distinct the confused knowledge of the cause that was acquired through the first step, he refers to his work on the agent mind (Liber de mente agente) in which he develops an account of the transformation of confused into distinct knowledge through the analysis of a given whole in terms of its parts. He presents this process as the specific ability of the human mind. Thus once more method as a means of acquiring knowledge is based on the cognitive structure of knowing subject rather than on the ontological structure of the object of knowledge. In his commentary on the Posterior Analytics Zabarella identified Aristotle’s proofs that the planets are near and that the moon is a sphere as instances of the regressus-method. Other examples of the same method he analyzed are Aristotle’s proof of the existence of “first matter” (materia prima) from substantial change and his proof of an “eternal first mover” (primus motor aeternus) from local motion (Wallace 1999, p. 338).