Imágenes de páginas
PDF
EPUB

disposition, and motions of the planetary system, as they were in his time represented according to the scheme of Ptolemy, he found the whole void of order, symmetry, and proportion; like a picture, as he expresses himself, made up of parts copied from different originals, which, not fitting each other, should rather represent a monster than a man. He therefore perused the writings of ancient philosophers, to see whether any more rational account had ever been proposed of the motions of the heavens. The first hint to this effect that he gained was from Cicero, who, in his Academical Questions,' acquaints us, that Nicetas, a Syracusan, had taught that the earth turns round on its axis, which, to a spectator on the earth's surface, makes the whole heavens appear daily to revolve. Afterwards, from Plutarch he found, that Philolaus had taught that the earth moved annually round the sun. He immediately perceived that, by allowing these two motions, all the perplexity, disorder, and confusion which had troubled him, in the celestial motions, vanished; and that, instead of them, a simple regular disposition of the whole, and a harmony of the motions appeared, worthy of the great Author of the world."

It ac

Now it is to be observed, that this theory of Copernicus was, in the first instance, a simple hypothesis. counted for the known appearances of the heavens; but those known appearances did not require it. For, in the system generally adopted at the time, that of Ptolemy, according to the natural suggestion as it may seem of human imagination, and which placed the earth in the centre of the world, there was nothing inconsistent with the then ascertained facts of the planetary motions. The choice was therefore between two hypotheses; and the reason for the preference of that of Copernicus was, not that it explained what was left unexplained by the other, but that one made the structure of our system perplexed and intricate, and the other reduced its motions to simple and beautiful order. But when this hypothesis had by its beautiful simplicity recommended its probability, then was science excited to find observations concurring with this hypothesis; and when numberless facts were ascertained which this hypothesis would explain and no other

when other later theories resting on their own grounds were found to agree with it-it was then considered as inductively demonstrated; yet all this weight of inductive evidence may be summed up in this, that each observation, severally taken and put in apposition, as Locke would say, with this theory, is perceived to coincide with it, and none to contradict it.-The evidence then of inductive reasoning is merely an aggregate of simple perceptions of coincidence.

It may thus be understood what is meant by inductive reasoning. Appearances are first observed, which is all the knowledge directly conveyed to us of any existence. These appearances are to be accounted for, and the hypothesis which explains them reduces them into knowledge. that hypothesis must, in the first instance, be matter of conjecture merely, and the comparison of various observations with it, and the perception of their coincidence, is the inductive reasoning which confirms it.

But

So far what we have seen is the discovery by induction of absolute facts of physical nature, which are so situated as to be out of the reach of our knowledge by direct observation, and this was the first point of discussion proposed. There is, however, another great result of the application of inductive reasoning to the observation of natural existence, that is, the discovery of the general laws by which nature is governed. But when philosophy speaks of the discovery of general laws, it is not to be understood as if it presumed to ascertain the power which determines action, or the true connexions in nature, which are not discernible by us-all that is meant by such discovery is the perception of harmonies in the system of being by the intellectual extension of the law of one appearance to many, or, as it is commonly expressed, by resolving particular into more general facts. Thus the knowledge of the true places of the bodies of our planetary system, and of the true orbits which the planets by their revolutions describe, are merely facts. When Newton showed that the course of those motions agreed with what must take place if they were determined by the same cause by which unsupported bodies fall, assigning gravitation as the principle which regulated the descent of heavy bodies

and the motion of planets, he gave no explanation of the cause, for the cause in both instances is equally unknownhe merely resolved the two unlike facts of the fall of bodies, and the deflexion of the planets' course from a right line, into one common fact or law, namely, that the bodies of matter tend towards one another. This more general law might be said to be a harmony found in nature connecting the events which take place on the surface of our globe and the motions of the planets in one system. The mere discovery of the same tendency of matter to matter, existing alike here and in the mutual relations of those vast worlds, is itself a wide embracing harmony; but that effects so unlike in appearance fall under one law is a harmony of another kind, a harmony of simplicity in the design by which the world is ordered. Even when within the limits of our own planet philosophy examines and analyses the various appearances and effects which fall under this common law of gravitation, tracing the operation of this one principle in the agency that has given to the earth its solidity, in the law appointed to the ocean alike to lift up its tides and to retain its waters in their bed, when it finds that by the same power the vapours are carried up and sustained in the floating clouds, and that by this the upward growth of all vegetation is determined, with numberless other effects in which the operation of this one principle is more or less disguised in its appearances when we see how many and various these results are, how much of the whole of the complex system of our knowledge and of our world they comprehend, we do not indeed obtain any knowledge of causation, but we resolve a vast diversity of facts under that one common fact, whatever its cause may be, that matter tends to matter. But in merely thus reducing these diverse effects under a common law, we cannot but feel that we have greatly enlarged the comprehension of our own intelligence; and with respect to our knowledge of the universe, we have acquired insight into the harmony of design in its constitution when we have seen one single principle employed, through so wide an extent of created existence, to produce effects so various from one another.

In this resolution of various appearances into universal laws, it is important to observe what is and what is not effected. There is no discovery of absolute causation, which is always hidden from our sight-what is obtained is the extended recognition of a single fact under a great diversity of appearances, viz. that matter tends towards matter. We had occasion to show in what manner a particular fact was ascertained, namely, by the proposal of a well-conceived hypothesis, and then by inductive reasoning justifying and confirming it. In the same manner, in the extension of a single fact through such variety of appearances, or its generalization, as it is called, there is the same process pursued. First is the bold conjecture of philosophy that this is indeed the common law which prevails through all these appearances, and next in order is that inductive reasoning which confirms and establishes the hypothesis. But if we ask in what that inductive reasoning consists, it is found as before that it consists in nothing more than an aggregate of intellectual perceptions of coincidence. It consists in the collection of innumerable minute and partial facts-of appearances among the subjects-in the comparison of them with the hypothesis, and the perception of their coincidence. The particular manner in which these innumerable confirming observations are pursued and ascertained does not need to be considered in the present enquiry. It is when they are ascertained that they become, with respect to that hypothesis, the matter of inductive reasoning.

It needs only further to be observed, that every general law thus ascertained, becomes a means of further discovery; because the philosopher expects other effects yet unexplained to fall under it, and strong in this discovery, he goes on to observe and to explore, that he may comprehend under the same knowledge what yet remains unknown. His process being merely this to observe individual facts, to generalize them, and then to advance again to the observation of further effects, to bring them under his known general law ;-but here too his induction is still the same, being never more than the comparison of one thing with another, and the perception of their coincidence.

In all these reasonings, however, there is never more attained than probability upon probability, infinitely accumulated. There can be no demonstration. The belief that is forced upon the mind is indeed irresistible. But the conviction yet remains, that under the weight of all this evidence there may yet by possibility be error. It is still remembered that “ no hypothesis, how numerous soever the facts may be with which it tallies, can completely exclude the possibility of exceptions or limitations, hitherto undiscovered." It is still considered, that our belief is grounded merely on the concurrence of numberless appearances coinciding with one Hypothesis; but that the absolute truth of the Hypothesis, or the connexion in nature in which it subsists, is placed out of the reach of our discovery.

Such then is the nature of inductive reasoning. We have taken the illustrations which were necessary to explain it, from the appearances, facts, and laws of the Physical world, because these are more simply and easily stated, and are more generally and indisputably recognised. But the process of inductive reasoning is the same with respect to the mind: all reasoning which is employed to establish its facts or its laws, from appearances collected by self-observation or observation of others, being precisely the same the aggregate result of many comparisons, and of intuitive perceptions upon such comparison made of disagreement or coincidence.

We have seen upon what grounds the belief of mathematical reasoning rests, namely, on the confidence of the mind in its perception of connexions among its own thoughts. We may now consider upon what grounds its belief in the reasonings of induction is established. In all inductive enquiry, then, the ground of our reasoning is a belief of constancy in the appointed order, and of unity in the design of nature. Our belief of constancy in the appointed order of nature, that is to say, the determination of our mind to conceive, that whatever it discerns to take place, takes place by established and permanent laws, and will therefore recur continually in like circumstances, appears to be, as we observed in speaking formerly on the relation of cause and effect, one of those inherent intellectual tendencies which are

originally impressed upon our minds in their constitution, and which are confirmed by the constant tenor of our experience. Upon the supposition of such a constancy, it is evident that all reliance upon our knowledge must be founded, since, if these laws could vary, the whole structure of our knowledge would be immediately overthrown. Upon this belief, then, rests our assurance that what we have ascertained is invariably true. The other element of our reasoning, namely, our belief of unity in the design of nature, may require to be more fully considered. This is the foundation of our reasoning by analogy, when, observing like appearances, the mind is irresistibly impelled to ascribe them to like causes an implanted tendency which all experience confirms. It is the ground of that expectation which carries us forward continually in philosophic investigation, and which is the whole spirit of philosophy, the expectation of reducing more and more facts under the laws already known, so as to enlarge continually the conception of the law itself, and to comprehend under the dominion of intellect more and more of the yet uncomprehended facts of the universe. Lastly, it is the true ground of our belief in our reasoning at all, because the sole evidence to us of truth in our reasonings is their harmony; but this harmony is evidence of their truth, only because we presuppose unity in the design of created things, and the harmony we find in our own thoughts appears to us to betoken a correspondence between them, and that believed unity of design in the constitution of the world. If it were possible for us to conceive diversity of purpose in the scheme of creation, we could never know that what we beheld in one part had any connexion with what we had known in another; we could not find, even in the consistency of our reasonings, a proof of their truth. It might be a proof of error.

Such then is the nature of inductive reasoning: a proceeding of the mind, not appertaining to science alone, but proper to the human intelligence from the beginning of its operations, accompanying it in all its steps, instructing those whose knowledge of the worlds physical and mental with which we are conversant is rudest and most unform

ed, and constituting the ground and basis of the structure of all the knowledge which we can acquire through life. But it is most celebrated in science, because there only it had been long wanting;-the intellect, in its self-confidence, lifting itself above the servitude of observation, and trusting by its own meditative powers, by its own self-contemplation, to divine the laws of the universe. A presumption which might well blend it to the discovery of truth. From this false imagination of its own capacities, and this misdirection of its intellectual power, it was called by the great teacher of the inductive philosophy, who considering the ineffectual results of the speculations with which the mind had so long occupied itself in vain, and not believing that the cause of that un-⚫ successful labour could be in the insufficiency of the powers of the mind, perceived that it was to be found in the method of the enquiry which philosophy had pursued, and first directed them to the true course of investigation, when he called them away from their self-deluding imaginations, by the first simple and sublime words of that work in which he laid down the true principles, which were to guide the human mind in the investigation of truth." Homo naturæ minister et in terpres tantum facit et intelligit quantum de naturæ ordine re vel mente observaverit, nec amplius scit aut potest."

Two great results attend the knowledge thus acquired; one the command which man thus possesses over the means which nature lays before him for his use, and which has been wonderfully exemplified in the discoveries and inventions of art which have since been made, and are continually augmenting; the other, the intelligent wonder with which we are carried to understand, according to the range of our limited observation, the wisdom in which the world is created—an understanding in which we are especially rich beyond all the intellectual treasures of antiquity.

Having thus considered both kinds of reasoning, demonstrative and inductive, let us in a few words sum up what has been said, by a comparison of the two with each other.

We found in demonstrative reasoning, exhibited in its purest form, in mathematical science, a twofold ground of certainty; the first in the subjects

All

of its reasonings, which being conceptions of the mind itself, are perfectly known to it; the other in the process of its reasonings, in which at every step the proof is intuitive. Hence it follows that from a few elements, a vast structure of science can be raised up by consecutive reasonings; because the science comprehends the whole of its data within itself; and combination may rise on combination without end truth continuing throughout as certain as that in which it began. It is therefore the most perfect example of the application of reasoning; the whole connected chain of truths from the beginning to the utmost length, to which it can be carried, depending solely upon the power of reasoning. that is necessary, is that no step of reasoning be omitted. If it is, there the certainty stops; and what follows hangs on nothing. The chain is broken. In inductive, probable, or contingent reasoning, the subjects not being framed by the mind, the essential conditions of their being are not known to it. Their existence, independent as it is of the reason that examines them, can be known to it at best imperfectly and uncertainly ;-and so far only as the primary knowledge itself is probably true, have the reasonings of induction a probability of truth. Let it be remembered, however, that the reasonings of inductive science, as far as reasoning is applied, must be as severely logical, as those of mathematical science. There is but one Logic. But because the primary and essential conditions of the subject are not known, not all certainly known at least, the reasoning can never proceed far from the premises without great risk of error. Recourse must be had constantly to knowledge, and all conclusions verified by various reference to known facts. No severity of reasoning can secure truth, without this continual return upon facts and comparison with nature; as on the other hand, the constant reference to facts will often rectify the omissions and the errors of reasoning. From these different grounds of mathematical and inductive science, it may be observed as a consequence, that, in mathematical reasoning, to demonstrate one supposition to be false, demonstrates a contrary supposition to be true; because the whole of the elements are comprehended in the case, as in that method of proof which is called the

reductio ad absurdum. But in reasoning on the subjects of nature (inductive or physical reasoning), there is no such proof. The demonstration of the falsehood of a supposition determines its rejection, and nothing more; because there may be always other unsuggested hypotheses. If all the possible hypotheses could be known, the rejection of all but one would be sufficient to establish the truth of that one, as in mathematics. Hence, too,

we may remark another characteristic difference between them, that in all mathematic reasoning, there are no degrees of evidence. Every proof is at once perfect certainty. There is no probability; there is only conviction. In inductive reasoning, on the other hand, are to be found all degrees of probability, from the lowest presumption to the most irresistible belief.

TO THE AUTHOR OF "THE METAPHYSICIAN," IN MESSRS BLACKWOOD'S MAGAZINE.

SIR, Without presuming even so much as a guess, to whom I deem it due to address this letter, under the designation expressed above; and, being, by advance of years, and still more by chronic indisposition, cut off from general reading, including that of periodicals; as well as denied the practicability of correspondence, unless in very rare cases, I owe to an accidental meeting with a friend, in the street, the knowledge of your Philosophical Speculations in Messrs Blackwood's Magazine.

With regard to these speculations, in the first place, here I desire to express to you my congratulation on the general tenor of philosophizing which you have therein put forth: In which praise, however, perhaps I am only offering a tribute to my own self-love, since the coincidence of your views, with my own before the public, is equally extensive and striking. By this observation, I do not in the least doubt that the matter is a pure coincidence; and that we have, each, treated the subject from the suggestions of his own mind. But, certainly, such an extent of coincidence ought naturally to lead to further consequences. And, if your life admits of following out the subject-(while mine must, in the course of nature, soon close)-it may be reserved for you to resuscitate the defunct interest, in this country, in Metaphysical researches.

And, now, I have to offer to you my due acknowledgments for your honourable assignment to me of the opposition which I first set up against the doctrine" of CONSCIOUSNESS," taught by the school of Reid: (Although, indeed, in that, I only justified, and enlarged upon, the sound doctrine of Locke) the denial of which was a badge of fallacy in the Reideian school. But while I confess I have always viewed my "Essay on Consciousness" as a store-house of facts for the use of a philosophic mind, I have been fully sensible of its poverty in other respects, owing to the extraordinary circumstances in which I elaborated that my original sin in pneumatology. And, having had no leisure to recast its style, I have suffered it to drift as a derelict. To it, however, I owe the early approbation and friendship of Dr Parr. And now owe, for your ingenuous quotation of it in your Metaphysics for August and October, the concurrence of which is gratifying to me in my decline.

From

But I am brought now, to express my wonder that, in thus doing justice to my by-gone work, you do not appear to be aware of the existence of my subsequent and legitimate writings. For it is in these that you may find a tenor of speculation, in a certain extent remarkably coincident with your own. this, of course, is to be excepted my views of the CATEGORY OF RELATION; including in that Category my theory of Visual Perception, which demonstrates Visible Outline to be a phenomenon of mind, it being a line of meeting and contrast between two sensations of different colours. As I conceive this analysis of visible lines to be the BASIS of the philosophy of the intercourse between the mind and external objects, I would earnestly commend it to your consideration. And, as I must suppose that you have not seen the work, I have forwarded to Messrs Blackwood a bound copy of it; which I beg you will accept, as addressed to you in the fly leaf.

You may find a very effective critique on this volume ("First Lines of the

« AnteriorContinuar »