as many scholars have observed, late medieval authors increasingly conceived of all of the four aristotelian causes after the model of efficient causes. this case-study on Francisco Suárez's theory of natural teleology examines what kinds of problems this general tendency to conceive of causes on the model of efficient causes gave rise to, when it came to account for natural teleology. even though Suárez can allow for distinctive final causes that satisfy his general theory of causes, or so i argue against the more pessimist conclusions of recent commentators, Suárez's theory of final causation is strictly speaking-and against his own confession-only applicable to the explanation of the teleology involved in the actions of finite rational agents, while the teleology displayed by natural processes can no longer be seen as a proper and univocal instance of final causation. in this, Suárez provides a striking example for how the increasing restriction of the notion of cause to the notion of the efficient cause brought late scholastic theories to a point where the notion of a final cause became unusable for what it was initially introduced: for the explanation of teleological phenomena.