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introduced, that they become objects of attention to the mind, and assume the form of propositions.
In consequence of these two analogies or coincidences, I should have been inclined to comprehend, under the general title of asioms, all the truths which have been hitherto under our review, if the common usage of our language had not, in a great measure, appropriated that appellation to the axioms of mathematics; and if the view of the subject which I have taken, did not render it necessary for me to direct the attention of my readers to the wide diversity between the branches of knowledge to which they are respectively subservient.
I was anxious also to prevent these truths from being all identified, in point of logical importance, under the same name. The fact is, that the one class, (in consequence of the relation in which they stand to the demonstrative conclusions of geometry,) are comparatively of so little moment, that the formal enumeration of them was a matter of choice rather than of necessity ; whereas the other class have unfortunately been raised, by the sceptical controversies of modern times, to a conspicuous rank in the philosophy of the human mind. I have thought it more advisable, therefore, to bestow on the latter an appropriate title of their own; without however going so far, as to reject altogether the phraseology of those who have annexed to the word axiom a more enlarged meaning than that which I have usually given to it. Little inconvenience, indeed, can arise from this latitude in the use of the term; provided only it be always confined to those ultimate laws of belief, which, although they form the first elements of human reason, cannot with propriety be ranked among the principles from which any
of our scientific conclusions are deduced. Corresponding to the extension which some late writers have given to axioms, is that of the province which they have assigned to intuition; a term which has been applied, by Dr. Beattie and others, not only to the power by which we perceive the truth of the axioms of geometry, but to that by which we recognise the authority of the fundamental laws of belief, when we hear them enunciated in language. My only objection to this use of the word is, that it is a departure from common practice : according to which, if I be not mistaken, the proper objects of intuition are propositions analogous to the axioms prefixed to Euclid's Elements. In some other respects, this innovation might perhaps be regarded as an improvement on the very limited and imperfect vocabulary of which we are able avail ourselves in our present discussions.*
According to Locke, we have the knowledge of our own existence by intui. tion; of the existence of God by demonstration, and of other things by sensation. -Book iv. chap. 9. § 2.
This use of the word intuition seems to be somewhat arbitrary. The reality of our own existence is a truth which bears as little analogy to the axioms of mathe. matics, as any other primary truth whatever. If the province of intuition, there.
To the class of truths which I have here called laws of belief, or elements of reason, the title of principles of common sense was long ago given by Father Buffier, whose language and doctrine concerning them bears a very striking resemblance to those of some of our later Scottish logicians. This, at least, strikes me as the meaning which these writers in general annex to the phrase ; although all of them have frequently employed it with a far greater degree of latitude. When thus limited in its acceptation, it is obviously liable, in point of scientific accuracy, to two very strong objections, both of which have been already sufficiently illustrated. The first is, that it applies the appellation of principles to laws of belief from which no inference can be deduced; the second, that it refers the origin of these laws to common sense.* _Nor is this phraseology more agreeable to popular use than to logical precision. If we were to suppose an individual whose conduct betrayed a disbelief of his own existence, or of his own identity, or of the reality of surrounding objects, it would by no means amount to an adequate description of his condition to say, that he was destitute of common sense. We should at once pronounce him to be destitute of reason, and would no longer consider him as a fit subject of discipline or of punishment. The former expression, indeed, would only imply that he was apt to fall into absurdities and improprieties in the coinmon concerns of life. To denominate, therefore, such laws of belief as we have now been considering, constituent elements of human reason, while it seems quite unexceptionable in point of technical distinctness, cannot be justly censured as the slightest deviation from our habitual forms of speech. On the same grounds, it may be fairly questioned, whether the word reason would not, on some occasions, be the best substitute which our language affords for intuition, in that enlarged acceptation which has been given to it of late. If not quite so definite and precise as might be wished, it would be at least employed in one of those significations in which it is already familiar to every ear: whereas the meaning of intuition, when used for the same purpose, is stretched very far beyond its ordinary limits. And in cases of this sort, where we have to choose between two terms, neither of which is altogether unexceptionable, it will be found much safer to trust to the context for restricting, in the reader's mind, what is too general, than for enlarging what use has accustomed us to interpret in a sense too narrow. fore, be extended as far as it has been carried by Locke in the fore going sentence, it will not be easy to give a good reason why it should not be enlarged a little farther. The words intuition and demonstration, it must not be forgotten, have, both of them, an etymological reference to the sense of seeing: and when we wish to express, in the strongest terms, the most complete evidence which can be set before the mind, we compare it to the light of noon-day :—in other words, we compare it to what Mr. Locke here attempts to degrade, by calling it the evidence of sensation.
See the preceding part of this section, with respect to the word principle; and the Account of Reid's Life, for some remarks on the proper meaning of the phrase common sense.
I must add, too, in opposition to the high authorities of Dr. Johnson and Dr. Beattie,t that, for many years past, reason has been very seldom used by philosophical writers, or indeed by correct writers of any description, as synonymous with the power of reasoning. To appeal to the light of human reason from the reasonings of the schools, is surely an expression to which no good objection can be made, on the score either of vagueness or of
novelty. Nor has the etymological affinity between these two words the slightest tendency to throw any obscurity on the foregoing expression. On the contrary, this affinity may be of use in some of our future arguments, by keeping constantly in view the close and inseparable connexion which will be afterwards shown to exist between the two different intellectual operations which are thus brought into immediate contrast.
The remarks which I have stated in the two preceding sections, comprehend every thing of essential importance which I have to offer on this article of logic. But the space which it has occupied for nearly half a century, in some of the most noted philosophical works which have appeared in Scotland, lays me under the necessity, before entering on a new topic, of introducing, in this place, a few critical strictures on the doctrines of my predecessors.
Continuation of the subject. Critical remarks on some late con
troversies to which it has given rise. Of the appeals which Dr. Reid and some other modern writers have made, in their Philosophical Discussions, to Common Sense, as a Criterion of Truth.
I OBSERved, in a form erpart of this work, that Dr. Reid acknowledges the Berkeleian system to be a logical consequence of the opinions universally admitted by the learned at the time when Berkeley wrote. In the earlier part of his own life, accordingly, he inforins us, that he was actually a convert to the scheme of immaterialism; a scheme which he probably considered as of a perfectly inoffensive tendency, as long as he conceived the existence of the material world to be the only point in dispute. Finding, however, from Mr. Hume's writings, that, along with this paradox, the
+ Dr. Johnson's definition of Reason was before quoted. The following is that given by Dr. Beattie :
“ Reason is used by those who are most accurate in distinguishing, to signify that power of the human mind by which we draw inferences, or by which we are convinced, that a relation belongs to two ideas, on account of our having found that these ideas bear certain relations to other ideas. In a word, it is that faculty which enables us, from relations or ideas that are known, to investigate such as are unknown, and without which we never could proceed in the discovery of truth a single step beyond first principles or intuitive axioms."-Essay on Truth, Part I. Chap. i.
ideal theory necessarily involved various other consequences of a very different nature, he was led to a careful examination of the data on which it rested: when he had the satisfaction to discover that its only foundation was a hypothesis, unsupported by any evidence whatever but the authority of the schools.*
From this important concession of a most impartial and competent judge, it may be assumed as a fact that, till the resutation of the ideal theory in his own “ Inquiry into the Human Mind,” the partizans of Berkeley's system remained complete masters of the controversial field; and yet, during the long period which intervened, it is well known how little impression that system made on the belief of our soundest philosophers. Many answers to it were attempted, in the meantime, by various authors, both in this country and on the Continent; and by one or other of these, the generality of the learned professed themselves to be convinced of its futility ;-the evidence of the conclusion (as in many other cases) supporting the premises, and not the premises the conclusion.f A very curious anecdote, in illustration of this, is mentioned in the life of Dr. Berkeley. After the publication of his book, it appears that he had an interview with Dr. Clarke ; in the course of which, Clarke, it is said, discovered a manifest unwillingness to enter into the discussion, and was accused by Berkeley of a want of candor.f—The story (which, if I recollect right, rests on the authority of Whiston) has every appearance of authenticity; for as Clarke, in common with his antagonist regarded the principles of the ideal theory as incontrovertible, it was perfectly impossible for him, with all his acuteness, to detect the flaw to which Berkeley's paradox owed its plausibility. In such circumstances, would it have been unphilosophical in Clarke to have defended himself, by saying: “Your conclusion not only contradicts those perceptions of my senses, the evidence of which I feel to be irresistible; but by annihilating space itself as an external existence, bids defiance to a conviction inseparable from the human understanding ; and, therefore, although I cannot point out the precise oversight which has led you astray, there must necessarily be some error, either in your original data, or in your subsequent reasoning.” Or, supposing Clarke to have perceived, as clearly as Reid, that Berkeley's reasoning was perfectly unexceptionable, might he not have added ;« The conclusion which it involves is a demonstration in the form of a reductio ad absurdum, of the unsoundness of the ideal theory, on which the whole of your argument is built ?"*
* It was not, therefore, (as has been very generally imagined by the followers of Berkeley) from any apprehension of danger in his argument against the exist. ence of matter, that Reid was induced to call in question the ideal theory ; but because he thought that Mr. Hume had clearly shown, by turning Berkeley's weapons against himself, that this theory was equally subversive of the existence of mind. The ultimate object of Berkeley and of Reid was precisely the same ; the one asserting the existence of matter from the very same motive which led the other to deny it.
When I speak of Reid's asserting the existence of matter, I do not allude to any new proofs which he has produced of the fact. This he rests on the evidence of sense, as he rests the existence of the mind on the evidence of consciousness. All that he professes to have done is, to show the inconclusiveness of Berkeley's argument against the former, and that of Hume against the latter, by refuting the ideal hypothesis which is the common foundation of both.
+ The impotent, though ingenious attempt of Berkeley (not many years after the date of his metaphysical publications) to shake the foundations of the newlyinvented method of Fluxions, created, in the public mind, a strong prejudice against him, as a sophistical and paradoxical disputant; and operated as a more powerful antidote to the scheme of immaterialism, than all the reasonings which his contemporaries were able to oppose to it. This unfavorable impression was afterwards not a little confirmed by the ridicule, which he incurred in consequence of his pamphlet on the Virtues of Tar-Water ; a performance, however, of which it is but justice to add, that it contains a great deal more, both of sound philosophy and of choice learning, than could have been expected from the subject.
# Philosophical Essays, p. 78.
That Clarke would look upon the Berkeleian theory with more than common feelings of suspicion and alarm, may be easily conceived, when it is recollected that, by denying the independent existence both of space and of time, it put an end at once to his celebrated argument à priori, for the existence of God.
I am far from supposing that Berkeley would have admitted this consideration as decisive of the point in dispute. On the contrary, it appears from his writings, that the scheme of immaterialism was, in his opinion, more agreeable to popular belief, than the received theories of philosophers concerning the independent existence of the external world; nay, that he considered it as one of the many advantages likely to result from the universal adoption of his system, that “men would thereby be reduced from paradoxes to common sense."
The question, however, if not decided by this discussion, would at least have been brought to a short and simple issue; for the paramount authority of the common sense or common reason of mankind being equally recognised by both parties, all that remained for their examination was,—whether the belief of the existence, or that of the non-existence of matter, was sanctioned by this supreme tribunal ? For ascertaining this point, nothing more was necessary than an accurate analysis of the meaning annexed to the word existence: which analysis would have at once shown, not only that
I acknowledge, very readily, that the force of this indirect mode of reasoning is essentially different in mathematics, from what it is in the other branches of knowledge; for the object of mathematics (as will afterwards more fully appear) x not being truth, but systematical connexion and consistency, whenever two contradictory propositions occur, embracing evidently the only possible suppositions on the point in question, if the one can be shown to be incompatible with the definitions or hypotheses on which the science is founded, this may be regarded as perfectly equivalent to a direct proof of the legitimacy of the opposite conclusion. In the other sciences, the force of a reductio ad absurdum depends entirely on the maxim, " That truth is always consistent with itself;" a maxim which, however certain, rests evidently on grounds of a more abstract and metaphysical nature than the indirect demonstrations of geometry. It is a maxim, at the same time, to which the most sceptical writers have not been able to refuse their testimony. “ Truth,” says Mr. Hume himself, “is one thing, but errors are numberless, and every man has a different one."
The unity, or systematical consistency of truth, is a subject which well deserves to be farther prosecuted. It involves many important consequences, of which Mr. Hume does not, from the general spirit of his philosophy, seem to have been sufficiently aware.