Final causality cannot be imagined without efficient causality; but no whit the less on that account are their modes of action polar contraries. The sheriff would still have his fist, even if there were no court; but an efficient cause, detached from a final cause in the form of a law, would not even possess efficiency: it might exert itself, and something might follow post hoc, but not propter hoc; for propter implies potential regularity. Now without law there is no regularity; and without the influence of ideas there is no potentiality.