  The most influential section in the Aristotelian tradition, where the relationship between the theoretical or speculative sciences is dealt with, is the beginning of Aristotle’s treatise On the Soul. Aristotle gives two criteria for the hierarchy: the dignity of their subject-matter and the exactness of their demonstrations. In his posthumous commentary on De anima Zabarella raises the question of the hierarchy of the sciences. In most cases, in Zabarella’s view, the science with a nobler subject-matter can be considered superior, but not always. All human knowledge can be compared and there are no grounds for giving either of these criteria absolute priority. In the contemplative sciences the nobility of the subject-matter should be considered superior to the causality of knowledge. In logic, however, where the instruments of science are considered, the nobler instrument is the one that is more precise and produces more certain knowledge.