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Sect. IV. The superiority of scientific evidence re-examined.
it is plain that we are in a great measure indebted to memory, and in some measure even to experience.
ARITHMETICAL operations, as well as geometrical, are in their nature scientific : yet the most accurate accountants are very sensible of the possibility of committing a blunder, and, therefore rarely fail, for Securing the matter, when it is of importance, to prove what they have done, by trying to effect the same thing another way. You have employed yourself, I suppose, in resolving some difficult problem by algebra, and are convinced that your solution is just. One whom you know to be an expert algebraist, carefully peruses the whole operation, and acquaints you that he hath discovered an error in your procedure. You are that instant sensible that your conviction was not of such an impregnable nature, but that his single testimony, in consequence of the confidence you repose in his experienced veracity and skill, makes a considerable abatement in it.
MANY cases might be supposed, of belief founded only on moral evidence, which it would be impossible thus to shake. A man of known probity and good sense, and (if you think it makes an addition of any moment in this case) an astronomer and philosopher, bids you look at the sun as it goes down, and tells you, with a serious countenance, that the sun which sets to-day will never again rise upon the earth. What would be the effect of this declaration ? Would it create in you any doubts? I believe it might, as to
Sect. II. Of deductive evidence.
the soundness of the man's intellects, but not as to the truth of what he said. Thus, if we regard only the effect, demonstration itself doth not always produce such immoveable certainty, as is sometimes consequent on merely moral evidence. And if there are, on the other hand, some well-known demonstrations, of so great authority, that it would equally look like lunacy to impugn, it may deserve the attention of the curious, to enquire how far, with respect to the bulk of mankind, these circumstances, their having stood the test of ages, their having obtained the universal suffrage of those who are qualified to examine them (things purely of the nature of moral evidence) have contributed to that unshaken faith with which they are received.
THE principal difference, then, in respect of the result of both kinds, is reduced to this narrow point. In mathematical reasoning, provided you are ascertained of the regular procedure of the mind, to affirm that the conclusion is false, implies a contradiction; in moral reasoning, though the procedure of the mind were quite unexceptionable, there still remains a physical possibility of the falsity of the conclusion. But how small this difference is in reality, any judicious person who but attends a little, may easily discover. The geometrician, for instance, can no more doubt, whether the book called Euclid's Elements, is a human composition, whether its contents were discovered and digested into the order in which they are there disposed, by human genius and art, than he can doubt
Sect. IV. The superiority of scientific evidence re-examined.
the truth of the propositions therein demonstrated. Is he in the smallest degree surer of any of the properties of the circle, than that if he take away his hand from the compasses, with which he is describing it on the wall, they will immediately fall to the ground. These things affect his mind, and influence his practice, precisely in the same manner.
So much for the various kinds of evidence, whether intuitive or deductive ; intuitive evidence, as divided into that of pure intellection, of consciousness, and of common sense, under the last of which that of memory is included; deductive evidence, as divided into scientific and moral, with the subdivisions of the latter into experience, analogy, and testimony, to which hath been added, the consideration of a mixed species concerning chances. So much for the various subjects of discourse, and the sorts of eviction of which they are respectively susceptible. This, though peculiarly the logician's province, is the foundation of all conviction, and consequently of persuasion too. To attain either of these ends, the speaker must always assume the character of the close and candid reasoner; for, though he may be an acute logician who is no orator, he will never be a consummate ora. tor who is no logician.
Of the nature and use of the scolastic art of Syllogiving.
HAviNG, in the preceding chapter, endeavoured to
trace the outlines of natural logic, perhaps with more . minuteness than in such an enquiry as this was strict
ly necessary, it might appear strange to pass over in silence the dialectic of the schools; an art which, though now fallen into disrepute, maintained, for a tract of ages, the highest reputation among the learned. What was so long regarded, as teaching the only legitimate use and application of our rational powers in the acquisition of knowledge, ought not surely, when we are employed in investigating the nature and the different sorts of evidence, to be altogether overlooked. - - - -
It is long since I was first convinced, by what Mr.
Locke hath said on the subject, that the syllogistic art, with its figures and moods, serves more to display the ingenuity of the inventor, and to exercise the address and fluency of the learner, that to assist the diligent inquirer in his researches after truth. The method of proving by syllogism, appears, even on a superficial review, both unnatural and prolix. The rules laid down for distinguishing the conclusive from the incon
Of the nature and use of the scholastic art of syllogizing.
clusive forms of argument, the true syllogism from the various kinds of sophism, are at once cumbersome to the memory, and unnecessary in practice. No person, one may venture to pronounce, will ever be made a reasoner, who stands in need of them. In a word, the whole bears the manifest indications of an artificial and ostentatious parade of learning, calculated for giving the appearance of great profundity, to what in fact is very shallow. Such, I acknowledge, have been, of a long time, my sentiments on the subject. On a nearer inspection, I cannot say I have found reason to alter them, though I think I have seen a little further into the nature of this disputative science, and consequently into the grounds of its futility. I shall, therefore, as briefly as possible, lay before the reader a few observations on the subject, and so dismiss this article.
PERMIT me only to premise, in general, that I proceed all along on the supposition, that the reader hath some previous acquaintance with school-logic. It would be extremely superfluous, in a work like this, to give even the shortest abridgment that could be made of an art so well known, and which is still to be found in many thousand volumes. On the other hand, it is not necessary that he be an adept in it, a mere smattering will sufficiently serve the present purpose.
My first observation is, that this method of arguing has not the least affinity to moral reasoning, the procedure in the one being the very reverse of that employed in the other. In moral reasoning we proceed