<P> (d) The same as "end"; i.e. the final cause; e.g., as the "end" of walking is health . For why does a man walk? "To be healthy", we say, and by saying this we consider that we have supplied the cause (the final cause). </P> <P> Aristotle further discerned two modes of causation: proper (prior) causation and accidental (chance) causation . All causes, proper and accidental, can be spoken as potential or as actual, particular or generic . The same language refers to the effects of causes, so that generic effects are assigned to generic causes, particular effects to particular causes, and actual effects to operating causes . </P> <P> Averting infinite regress, Aristotle inferred the first mover--an unmoved mover . The first mover's motion, too, must have been caused, but, being an unmoved mover, must have moved only toward a particular goal or desire . </P> <P> In line with Aristotelian cosmology, Thomas Aquinas posed a hierarchy prioritizing Aristotle's four causes: "final> efficient> material> formal". Aquinas sought to identify the first efficient cause--now simply first cause--as everyone would agree, said Aquinas, to call it God . Later in the Middle Ages, many scholars conceded that the first cause was God, but explained that many earthly events occur within God's design or plan, and thereby scholars sought freedom to investigate the numerous secondary causes . </P>

For hume the necessary conditions for causality are