  What should become evident during this survey is the extremely tight and complex interconnection between medieval causal theories and medieval ontology. After Aristotle’s texts had been assimilated, almost all medieval academic theories had an ontology which was basically hylomorphic: substances were composites of matter and form, and change was described as the loss of one form and the acquisition of another.  Form was not merely shape, but an active principle: the form of a thing was responsible for its causal role (White 1984; Goddu 1999, p. 148).  Furthermore, in any causal interaction, the allocation of active and passive roles to the individuals involved tended to be thought of as unproblematic. Although many aspects of Aristotle’s causal theories were extensively and critically debated, this basic hylomorphism persisted throughout; and it is this, rather than anything more arcane, which often poses the greatest problems in assimilating, or evaluating, medieval thought on these topics.