A System of Logic: Ratiocinative and Inductive Volume II Part 21

The attempts, for instance, to disprove the population doctrines of Malthus, have been mostly cases of _ignoratio elenchi_. Malthus has been supposed to be refuted if it could be shown that in some countries or ages population has been nearly stationary; as if he had a.s.serted that population always increases in a given ratio, or had not expressly declared that it increases only in so far as it is not restrained by prudence, or kept down by poverty and disease. Or, perhaps, a collection of facts is produced to prove that in some one country the people are better off with a dense population than they are in another country with a thin one; or that the people have become more numerous and better off at the same time. As if the a.s.sertion were that a dense population could not possibly be well off: as if it were not part of the very doctrine, and essential to it, that where there is a more abundant capital there may be a greater population without any increase of poverty, or even with a diminution of it.

The favourite argument against Berkeley's theory of the non-existence of matter, and the most popularly effective, next to a "grin"[38]--an argument, moreover, which is not confined to "c.o.xcombs," nor to men like Samuel Johnson, whose greatly overrated ability certainly did not lie in the direction of metaphysical speculation, but is the stock argument of the Scotch school of metaphysicians--is a palpable _ignoratio elenchi_.

The argument is perhaps as frequently expressed by gesture as by words, and one of its commonest forms consists in knocking a stick against the ground. This short and easy confutation overlooks the fact, that in denying matter, Berkeley did not deny anything to which our senses bear witness, and therefore cannot be answered by any appeal to them. His scepticism related to the supposed substratum, or hidden cause of the appearances perceived by our senses: the evidence of which, whatever may be thought of its conclusiveness, is certainly not the evidence of sense. And it will always remain a signal proof of the want of metaphysical profundity of Reid, Stewart, and, I am sorry to add, of Brown, that they should have persisted in a.s.serting that Berkeley, if he believed his own doctrine, was bound to walk into the kennel, or run his head against a post. As if persons who do not recognise an occult cause of their sensations, could not possibly believe that a fixed order subsists among the sensations themselves. Such a want of comprehension of the distinction between a thing and its sensible manifestation, or, in metaphysical language, between the noumenon and the phenomenon, would be impossible to even the dullest disciple of Kant or Coleridge.

It would be easy to add a greater number of examples of this fallacy, as well as of the others which I have attempted to characterize. But a more copious exemplification does not seem to be necessary; and the intelligent reader will have little difficulty in adding to the catalogue from his own reading and experience. We shall therefore here close our exposition of the general principles of logic, and proceed to the supplementary inquiry which is necessary to complete our design.

FOOTNOTES:

[1] Supra, p. 204.

[2] _Vulgar Errors_, book v. chap. 21.

[3] _Pharmacologia_, Historical Introduction, p. 16.

[4] The author of one of the Bridgewater Treatises has fallen, as it seems to me, into a similar fallacy when, after arguing in rather a curious way to prove that matter may exist without any of the known properties of matter, and may therefore be changeable, he concludes that it cannot be eternal, because "eternal (pa.s.sive) existence necessarily involves incapability of change." I believe it would be difficult to point out any other connexion between the facts of eternity and unchangeableness, than a strong a.s.sociation between the two ideas. Most of the _ priori_ arguments, both religious and anti-religious, on the origin of things, are fallacies drawn from the same source.

[5] Supra, book ii. chap. v. 6, and ch. vii. 1, 2, 3. See also _Examination of Sir William Hamilton's Philosophy_, chap. vi. and elsewhere.

[6] I quote this pa.s.sage from Playfair's celebrated _Dissertations on the Progress of Mathematical and Physical Science_.

[7] This statement I must now correct, as too unqualified. The maxim in question was maintained with full conviction by no less an authority than Sir William Hamilton. See my _Examination_, chap. xxiv.

[8] _Nouveaux Essais sur l'Entendement Humain--Avant-propos_.

(uvres, Paris ed. 1842, vol. i. p. 19.)

[9] This doctrine also was accepted as true, and conclusions were grounded on it, by Sir William Hamilton. See _Examination_, chap. xxiv.

[10] Not that of Leibnitz, but the principle commonly appealed to under that name by mathematicians.

[11] _Dissertation_, ut supra, p. 27.

[12] _Hist. Ind. Sc._ Book i. chap. i.

[13] _Novum Organum_, Aph. 75.

[14] Supra, book iii. ch. vii. 4.

[15] It is hardly needful to remark that nothing is here intended to be said against the possibility at some future period of making gold; by first discovering it to be a compound, and putting together its different elements or ingredients. But this is a totally different idea from that of the seekers of the grand arcanum.

[16] _Pharmacologia_, pp. 43-5.

[17] Vol. i. chap. 8.

[18] _Nov. Org._, Aph. 46.

[19] Playfair's _Dissertation_, sect. 4.

[20] _Nov. Org. Renov._, p. 61.

[21] _Pharmacologia_, p. 21.

[22] _Pharmacologia_, pp. 23-4.

[23] Ibid. p. 28.

[24] Ibid. p. 62.

[25] _Pharmacologia_, pp. 61-2.

[26] Supra, p. 182.

[27] _Elements of the Philosophy of the Mind_, vol. ii. ch. 4, sect. 5.

[28] "Thus Fourcroy," says Dr. Paris, "explained the operation of mercury by its specific gravity, and the advocates of this doctrine favoured the general introduction of the preparations of iron, especially in scirrhus of the spleen or liver, upon the same hypothetical principle; for, say they, whatever is most forcible in removing the obstruction must be the most proper instrument of cure; such is steel, which, besides the attenuating power with which it is furnished, has still a greater force in this case from the gravity of its particles, which, being seven times specifically heavier than any vegetable, acts in proportion with a stronger impulse, and therefore is a more powerful deobstruent. This may be taken as a specimen of the style in which these mechanical physicians reasoned and practised."--_Pharmacologia_, pp. 38-9.

[29] _Pharmacologia_, pp. 39, 40.

[30] I quote from Dr. Whewell's _Hist. Ind. Sc._ 3rd ed. i. 129.

[31] _Hist. Ind. Sc._ i. 52.

[32] _Nov. Org._ Aph. 60.

[33] "An advocate," says Mr. De Morgan (_Formal Logic_, p. 270), "is sometimes guilty of the argument _ dicto secundum quid ad dictum simpliciter_: it is his business to do for his client all that his client might _honestly_ do for himself. Is not the word in italics frequently omitted? _Might_ any man honestly try to do for himself all that counsel frequently try to do for him? We are often reminded of the two men who stole the leg of mutton; one could swear he had not got it, the other that he had not taken it. The counsel is doing his duty by his client, the client has left the matter to his counsel. Between the unexecuted intention of the client, and the unintended execution of the counsel, there may be a wrong done, and, if we are to believe the usual maxims, no wrong-doer."

The same writer justly remarks (p. 251) that there is a converse fallacy, _ dicto simpliciter ad dictum secundum quid_, called by the scholastic logicians, _fallacia accidentis_; and another which may be called _ dicto secundum quid ad dictum secundum alterum quid_ (p. 265).

For apt instances of both, I must refer the reader to Mr. De Morgan's able chapter on Fallacies.

[34] An example of this fallacy is the popular error that _strong_ drink must be a cause of _strength_. There is here fallacy within fallacy; for granting that the words "strong" and "strength" were not (as they are) applied in a totally different sense to fermented liquors and to the human body, there would still be involved the error of supposing that an effect must be like its cause; that the conditions of a phenomenon are likely to resemble the phenomenon itself; which we have already treated of as an _ priori_ fallacy of the first rank. As well might it be supposed that a strong poison will make the person who takes it, strong.

[35] In his later editions, Archbishop Whately confines the name of Pet.i.tio Principii "to those cases in which one of the premises either is manifestly the same in sense with the conclusion, or is actually proved from it, or is such as the persons you are addressing are not likely to know, or to admit, except as an inference from the conclusion: as, _e.g._ if any one should infer the authenticity of a certain history, from its recording such and such facts, the reality of which rests on the evidence of that history."

[36] No longer even a probable hypothesis, since the establishment of the atomic theory; it being now certain that the integral particles of different substances gravitate unequally. It is true that these particles, though real _minima_ for the purposes of chemical combination, may not be the ultimate particles of the substance; and this doubt alone renders the hypothesis admissible, even as an hypothesis.

[37] _Hist. Ind. Sc._ i. 34.

[38] "And c.o.xcombs vanquish Berkeley with a grin."

BOOK VI.

ON THE LOGIC OF THE MORAL SCIENCES.

"Si l'homme peut prdire, avec une a.s.surance presque entire, les phnomnes dont il connat les lois; si lors mme qu'elles lui sont inconnues, il peut, d'aprs l'exprience, prvoir avec une grande probabilit les vnemens de l'avenir; pourquoi regarderait-on comme une entreprise chimrique, celle de tracer avec quelque vraisemblance le tableau des destines futures de l'espce humaine, d'aprs les rsultats de son histoire? Le seul fondement de croyance dans les sciences naturelles, est cette ide, que les lois gnrales, connues ou ignores, qui rglent les phnomnes de l'univers, sont ncessaires et constantes; et par quelle raison ce principe serait-il moins vrai pour le dveloppement des facults intellectuelles et morales de l'homme, que pour les autres oprations de la nature? Enfin, puisque des opinions formes d'aprs l'exprience ... sont la seule rgle de la conduite des hommes les plus sages, pourquoi interdirait-on au philosophe d'appuyer ses conjectures sur cette mme base, pourvu qu'il ne leur attribue pas une cert.i.tude suprieure celle qui peut natre du nombre, de la constance, de l'exact.i.tude des observations?"--CONDORCET, _Esquisse d'un Tableau Historique des Progrs de l'Esprit Humain_.