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causes themselves: in other words, we shall not confound physical causes with moral agency; but shall be prepared, in the only sound and legitimate way, to deduce the indications of the latter from the former.
The term "final cause," employed in the sense at first explained, as that which it must in strictness bear; viz., as involving a reference to the processes of creative intelligence; is doubtless most improperly introduced into the investigation by which we advance to the elementary truths of natural philosophy. And manifestly for this reason, that it expresses, and thus misleads us into making the assumption of the very thing which it ought to be our object to prove from the truths elicited by natural science; viz., the existence of creative intelligence, of an omnipotent and omniscient Creator.
But it has been contended that the study of "final causes" may be, and has been, of important use in physical discovery: and the well-known example is adduced of the discovery of the circulation of the blood by Harvey, in consequence of a reflection into which he was led on the probable use of the valves in the veins.
Let us keep to unambiguous terms, and the case merely shows that a good conjecture, derived from the observed fitness of the valves for such an office as would be discharged by them, if the circulation were a fact, led him to the right train of analogy, which he so completely verified by observation. In this way
it is often the case in the researches of the naturalist, that from observing the obvious purpose of some one organ, he is able to conjecture the probable use of some other, which, but for such analogy, would be totally obscure; and such conjectures, if well founded, seldom fail to be borne out by actual experimental proof.
The uses of things (simply so considered,) wherever they have been fairly traced and established, supply a perfectly just, and most useful ground of analogy for guiding us to inductive conclusions. The habit of observing such adaptations in actual cases suggests grounds of reasonable probability for expecting them in instances as yet untried; and such conjectures in skilful hands are of the utmost utility in physical inquiries; as we often noticed, in the course of our former illustrations.
So long, then, as we confine ourselves to the simple notion of the fact of adjustment, or use, without reference to moral or intellectual causation, we are not departing from sound physical analogies, which we have before contended are the only rational guides in those conjectures which lead to sound inductions.
The Economy of Causes.
ANOTHER instance of the use of final causes in physical investigation, on which much stress has been sometimes laid, is the reference to what has been
called the "lex parsimonia," the "economy of causes," or the principle that "nature does nothing in vain;" or that the most simple means are always adopted for obtaining given ends; or that several powers or agents are never resorted to where one suffices. Such a principle finds its use and application in aid of scientific research, when it is taken as a guide to the more simple in preference to the more complex theory; to known causes rather than imaginary; to hypotheses already applying in other cases rather than new and arbitrary ones; to analogies with existing and established relations rather than to gratuitous suppositions.
Of this kind were the arguments from probability, which weighed most with Copernicus and with Galileo, in favour of the solar system, at a period when no demonstration had been attained; and a more precise exemplification has been found in the argument for the earth's motion in its orbit, and its rotation on its axis, being derived from one and the same primary impulse. It having being shown by Bernouilli, on mechanical principles, that one impulse would produce both, and even the precise point of the earth calculated at which it must have been applied, so as to accord with the existing motions and velocities.
Upon this I will merely observe that the principle referred to, when stated in simple and precise terms, is, in fact, nothing more than the announcement of a great physical and inductive law, the
evidence for which is no other than that of any other physical induction. It is, however, highly important in our mode of enunciating it, to keep it carefully distinct, as an inductive conclusion, from all manner of speculative assumptions. For (precisely as we have noticed in other cases) it is in this way alone that we can consistently and rationally employ any guide to scientific conclusions, when those very conclusions are to form the evidence of the truths of natural theology. For the legitimate force of such arguments, it is manifestly essential that we avoid making them arguments in a circle; and that we do not assume the operation of the Divine will in the process of reasoning by which we seek to prove the operation of the Divine will.
Final Causes in Comparative Physiology.
THE question respecting the introduction of final causes into philosophy has been made peculiarly prominent in the controversy which has subsisted between two distinguished schools of physiology in France, to whose general views of organization we have already adverted*. The question with regard to final causes has, in fact, been mixed up with the purely physiological question at issue between them, from which it undoubtedly is quite distinct, and ought, especially in an inquiry like the present, to be
* See Whewell's History of the Inductive Sciences, vol. iii. p. 456, et seq.; and above, p. 39.
carefully kept so. In the views which have been taken of this controversy, we may also observe that the tendency ascribed to the respective opinions has had a considerable share in influencing the judgment formed upon them; and has, perhaps, assisted in obscuring their real character; which, when dispassionately examined, seems to me by no means such as to justify the strong censure of the one and preference of the other, which has been sometimes expressed.
Cuvier and his followers have insisted strongly on the propriety of pursuing physiological examination upon the assumption, that every part of the organization of an animal must have some use, and that then by comparison of one part with another, we should proceed to trace the particular use and intention of each organ, and so advance to our conclusion as to the nature of the animal, and its place in the scale of creation. Cuvier specifically states this principle of what he terms "the conditions of existence," as equivalent to what are commonly called "final causes;" and speaks of the combination of organs adapted to " the part which the animal has to play in nature." And in affirming this, Cuvier has but extended and followed up the method of the most distinguished of his predecessors, who have generally regarded this adaptation of parts in organized structures as not only an inference deduced from all researches, but a sure guide in further investigations.