  We often find in Aristotle and in the literature influenced by him an enumeration of four types of cause: formal, material, efficient and final. The first two are uses of ‘cause’ in a somewhat wider sense than is current nowadays: the term here simply means ‘explanation in general’ (Ockham, Expositio Physicorum II, c11: Opera Philosophica IV, p. 348), and explanations by means of matter and form were common both in Aristotle and in the literature. Efficient causes are what we would now simply call ‘causes’. Final causes, however, are problematic: a final cause is an end or a purpose, and, whereas it is clear that rational agents act for the sake of ends, it is not clear that much else does. Furthermore, it also seems clear to us that the causality of a rationally pursued goal can be reduced to efficient causality.