must cool; when cooled they must become water and sink downwards."[1]
In scientific enquiry final causes are not to be absolutely condemned. Without reference to the final causes of the valves in the veins, Harvey would, perhaps, never have been able to discover the circulation of the blood. But the employment of final causes in the solution of biological problems is quite different from their employment in the solution of physical problems. Life involves a distinction of kind. Even in physical problems, however, a reference to final causes is frequently illuminating. It is the function of a watch to record fixed intervals of time—once this is understood, we are better able to appreciate the significance of each part of its mechanism. Be that as it may, a limit must be placed to the use of final causes. What that limit is may be doubtful, but this at least is certain—that Aristotle transgresses it, for we have already seen the frequent error in which the use of final causes has involved him. Very frequently in Aristotle's practice final causes are alone advanced, and immediate, proximate causes neglected.
Aristotle does not argue from final causes to the existence of a creative God previously existing and external to the universe. The universe has existed from all eternity. Marks of design in the universe are explained by Aristotle's 'Nature.' 'Nature' works toward an end, does nothing in vain, "does not act with conscious prevision,"[2] is "an indwelling power which pervades all things,"[3] "the instinct of the universe,"[4] a deus ex machina, and an enigma.
While rash generalisation without verification involves, as we have seen, for example, in Aristotle's use of final causes, a tendency to frequent error, it implies one thing indispensable to inductive procedure, viz., hypothesis. "Sagacity (ἄγχινοια)," says Aristotle,[5] "is a certain happy extempore conjecture (ἐυστοχίατις) of the middle term, as if a man perceiving that the moon always has that part lustrous which is towards the sun, should
