  The medieval literature is far from unanimous on these questions. William of Ockham, for example, who wrote several commentaries on Aristotle’s Physics, and who discusses these questions at numerous places in his commentary on Aristotle’s Physics, hardly has a uniform position. He is quite happy with explanations of natural phenomena by means of efficient causes in general, but he will also often speak of final causes: what is unclear is whether the final causes he speaks of (with varying degrees of strength in different works) have any explanatory role to play that cannot be reduced to efficient causality (Adams 1998; cf. Goddu 1999).