  However, Zabarella was not concerned solely with the separation between the theoretical sciences and the practical and productive disciplines, but dealt also with the relationships and hierarchy among the theoretical sciences themselves. The contemplative or speculative sciences, for Zabarella, are in Aristotelian manner only three in number: divine science, also called metaphysics, mathematics, and natural philosophy. Zabarella presents these contemplative sciences as being the only defenders of true knowledge. Zabarella emphasised in many instances that each speculative science should demonstrate their own principles and not borrow them from metaphysics. According to Zabarella, each discipline can be distinguished from others either with respect to the object considered (res considerata) or with respect to the way of considering (modus considerandi) (Pozzo 1998).  Natural philosophy, which deals with corporeal beings that have an inner principle of movement, differs from metaphysics (which contemplates being as being) and from mathematics (which deals with abstracted beings) in both ways. As a result, natural philosophy is autonomous and independent of both the other contemplative sciences.