289. Causes of Being. -- The study of causes is pursued on the lines laid down by Aristotle (44). Being, whether in its substantial or accidental state, exists in its causes or in potency before appearing in act or in reality.^{1} This realization, which is effected by motion or change, it is beyond the power of any being to confer on itself: "Quidquid movetur ab alio movetur" (efficient cause). The doctrine of creation modifies the Aristotelian theory of the eternity of matter and motion. Under the influence of the efficient cause, the subject (matter) receives the perfection (form) for which it had the capacity. By their mutual union and intercommunication, these latter -- the receiving subject and the received determination -- exercise a constitutive causality on the new being, or on its new state. They are constituent causes of the being, either of its very substantiality (primary material cause, formal substantial cause), or of some of the modes consequent on its substantiality (secondary material cause, accidental formal cause). The efficient cause is influenced by some realizable good (final cause), for the actual realization of which it exercises its efficiency. This stimulation of efficiency by finality is manifested more especially in the marvellous order and beauty of the universe. Were order the exception, it might be the result of some chance convergence of motor causes. But its actual permanence in time and universality in space, are alike inexplicable unless by means of an internal tendency which, being implanted in the acting causes, secures their constant co-ordination in carrying out the designs of nature. Thus, the scholastic teaching on finality completes the philosophy of being.

{1} "Quamvis autem causae sint quatuor, tres tamen earum, scilicet, efficiens formalis et finalis concurrunt in idem, unde relinquitur quod ordo naturac sit duplex, unus quidem secundum rationem causae materialis. . . . Alius autem ordo naturae est secundum rationem aliarum trium causarum, secundum quam perfectum est prius imperfecto et actus potentia" (Sr. THOMAS, Quodl., a. 19, c.).