A System of Logic: Ratiocinative and Inductive Volume I Part 10

[12] "Nous savons qu'il existe quelque chose hors de nous, parceque nous ne pouvons expliquer nos perceptions sans les rattacher des causes distinctes de nous-mmes; nous savons de plus que ces causes, dont nous ne connaissons pas d'ailleurs l'essence, produisent les effets les plus variables, les plus divers, et mme les plus contraires, selon qu'elles rencontrent telle nature ou telle disposition du sujet. Mais savons-nous quelque chose de plus? et mme, vu le caractre indtermin des causes que nous concevons dans les corps, y a-t-il quelque chose de plus savoir? Y a-t-il lieu de nous enqurir si nous percevons les choses telles qu'elles sont? Non videmment.... Je ne dis pas que le problme est insoluble, _je dis qu'il est absurde et enferme une contradiction_.

Nous _ne savons pas ce que ces causes sont en elles-mmes_, et la raison nous dfend de chercher le connatre: mais il est bien vident _ priori_, qu'_elles ne sont pas en elles-mmes ce qu'elles sont par rapport nous_, puisque la prsence du sujet modifie ncessairement leur action. Supprimez tout sujet sentant, il est certain que ces causes agiraient encore puisqu'elles continueraient d'exister; mais elles agiraient autrement; elles seraient encore des qualits et des proprits, mais qui ne ressembleraient rien de ce que nous connaissons. Le feu ne manifesterait plus aucune des proprits que nous lui connaissons: que serait-il? C'est ce que nous ne saurons jamais.

_C'est d'ailleurs peut-tre un problme qui ne rpugne pas seulement la nature de notre esprit, mais l'essence mme des choses._ Quand mme en effet on supprimerait par la pense tous les sujets sentants, il faudrait encore admettre que nul corps ne manifesterait ses proprits autrement qu'en relation avec un sujet quelconque, et dans ce cas _ses proprits ne seraient encore que relatives_: en sorte qu'il me parat fort raisonnable d'admettre que les proprits dtermines des corps n'existent pas indpendamment d'un sujet quelconque, et que quand on demande si les proprits de la matire sont telles que nous les percevons, il faudrait voir auparavant si elles sont en tant que dtermines, et dans quel sens il est vrai de dire qu'elles sont."--_Cours d'Histoire de la Philosophie Morale au 18me sicle_, 8me leon.

[13] An attempt, indeed, has been made by Reid and others, to establish that although some of the properties we ascribe to objects exist only in our sensations, others exist in the things themselves, being such as cannot possibly be copies of any impression upon the senses; and they ask, from what sensations our notions of extension and figure have been derived? The gauntlet thrown down by Reid was taken up by Brown, who, applying greater powers of a.n.a.lysis than had previously been applied to the notions of extension and figure, pointed out that the sensations from which those notions are derived, are sensations of touch, combined with sensations of a cla.s.s previously too little adverted to by metaphysicians, those which have their seat in our muscular frame. His a.n.a.lysis, which was adopted and followed up by James Mill, has been further and greatly improved upon in Professor Bain's profound work, _The Senses and the Intellect_, and in the chapters on "Perception" of a work of eminent a.n.a.lytic power, Mr. Herbert Spencer's _Principles of Psychology_.

On this point M. Cousin may again be cited in favour of the better doctrine. M. Cousin recognises, in opposition to Reid, the essential subjectivity of our conceptions of what are called the primary qualities of matter, as extension, solidity, &c., equally with those of colour, heat, and the remainder of the so-called secondary qualities.--_Cours_, ut supra, 9me leon.

[14] This doctrine, which is the most complete form of the philosophical theory known as the Relativity of Human Knowledge, has, since the recent revival in this country of an active interest in metaphysical speculation, been the subject of a greatly increased amount of discussion and controversy; and dissentients have manifested themselves in considerably greater number than I had any knowledge of when the pa.s.sage in the text was written. The doctrine has been attacked from two sides. Some thinkers, among whom are the late Professor Ferrier, in his _Inst.i.tutes of Metaphysic_, and Professor John Grote in his _Exploratio Philosophica_, appear to deny altogether the reality of Noumena, or Things in themselves--of an unknowable substratum or support for the sensations which we experience, and which, according to the theory, const.i.tute all our knowledge of an external world. It seems to me, however, that in Professor Grote's case at least, the denial of Noumena is only apparent, and that he does not essentially differ from the other cla.s.s of objectors, including Mr. Bailey in his valuable _Letters on the Philosophy of the Human Mind_, and (in spite of the striking pa.s.sage quoted in the text) also Sir William Hamilton, who contend for a direct knowledge by the human mind of more than the sensations--of certain attributes or properties as they exist not in us, but in the Things themselves.

With the first of these opinions, that which denies Noumena, I have, as a metaphysician, no quarrel; but, whether it be true or false, it is irrelevant to Logic. And since all the forms of language are in contradiction to it, nothing but confusion could result from its unnecessary introduction into a treatise, every essential doctrine of which could stand equally well with the opposite and accredited opinion.

The other and rival doctrine, that of a direct perception or intuitive knowledge of the outward object as it is in itself, considered as distinct from the sensations we receive from it, is of far greater practical moment. But even this question, depending on the nature and laws of Intuitive Knowledge, is not within the province of Logic. For the grounds of my own opinion concerning it, I must content myself with referring to a work already mentioned--_An Examination of Sir William Hamilton's Philosophy_; several chapters of which are devoted to a full discussion of the questions and theories relating to the supposed direct perception of external objects.

[15] _a.n.a.lysis of the Human Mind_, i. 126 et seq.

[16] It may, however, be considered as equivalent to an universal proposition with a different predicate, viz. "All wine is good _qu_ wine," or "is good in respect of the qualities which const.i.tute it wine."

[17] Dr. Whewell (_Philosophy of Discovery_, p. 242) questions this statement, and asks, "Are we to say that a mole cannot dig the ground, except he has an idea of the ground, and of the snout and paws with which he digs it?" I do not know what pa.s.ses in a mole's mind, nor what amount of mental apprehension may or may not accompany his instinctive actions. But a human being does not use a spade by instinct; and he certainly could not use it unless he had knowledge of a spade, and of the earth which he uses it upon.

[18] "From hence also this may be deduced, that the first truths were arbitrarily made by those that first of all imposed names upon things, or received them from the imposition of others. For it is true (for example) that _man is a living creature_, but it is for this reason, that it pleased men to impose both these names on the same thing."--_Computation or Logic_, ch. iii. sect. 8.

[19] "Men are subject to err not only in affirming and denying, but also in perception, and in silent cogitation.... Tacit errors, or the errors of sense and cogitation, are made by pa.s.sing from one imagination to the imagination of another different thing; or by feigning that to be past, or future, which never was, nor ever shall be; as when by seeing the image of the sun in water, we imagine the sun itself to be there; or by seeing swords, that there has been, or shall be, fighting, because it uses to be so for the most part; or when from promises we feign the mind of the promiser to be such and such; or, lastly, when from any sign we vainly imagine something to be signified which is not. And errors of this sort are common to all things that have sense."--_Computation or Logic_, ch. v. sect. 1.

[20] Ch. iii. sect. 3.

[21] To the preceding statement it has been objected, that "we naturally construe the subject of a proposition in its extension, and the predicate (which therefore may be an adjective) in its intension, (connotation): and that consequently coexistence of attributes does not, any more than the opposite theory of equation of groups, correspond with the living processes of thought and language." I acknowledge the distinction here drawn, which, indeed, I had myself laid down and exemplified a few pages back (p. 104). But though it is true that we naturally "construe the subject of a proposition in its extension," this extension, or in other words, the extent of the cla.s.s denoted by the name, is not apprehended or indicated directly. It is both apprehended and indicated solely through the attributes. In the "living processes of thought and language" the extension, though in this case really thought of (which in the case of the predicate it is not), is thought of only through the medium of what my acute and courteous critic terms the "intension."

For further ill.u.s.trations of this subject, see _Examination of Sir William Hamilton's Philosophy_, ch. xxii.

[22] Book iv. ch. vii.

[23] The doctrines which prevented the real meaning of Essences from being understood, had not a.s.sumed so settled a shape in the time of Aristotle and his immediate followers, as was afterwards given to them by the Realists of the middle ages. Aristotle himself (in his Treatise on the Categories) expressly denies that the _de?te?a? ??s?a?_, or Substanti Secund, inhere in a subject. They are only, he says, predicated of it.

[24] The always acute and often profound author of _An Outline of Sematology_ (Mr. B. H. Smart) justly says, "Locke will be much more intelligible if, in the majority of places, we subst.i.tute 'the knowledge of' for what he calls 'the Idea of'" (p. 10). Among the many criticisms on Locke's use of the word Idea, this is the one which, as it appears to me, most nearly hits the mark; and I quote it for the additional reason that it precisely expresses the point of difference respecting the import of Propositions, between my view and what I have spoken of as the Conceptualist view of them. Where a Conceptualist says that a name or a proposition expresses our Idea of a thing, I should generally say (instead of our Idea) our Knowledge, or Belief, concerning the thing itself.

[25] This distinction corresponds to that which is drawn by Kant and other metaphysicians between what they term _a.n.a.lytic_, and _synthetic_, judgments; the former being those which can be evolved from the meaning of the terms used.

[26] If we allow a differentia to what is not really a species. For the distinction of Kinds, in the sense explained by us, not being in any way applicable to attributes, it of course follows that although attributes may be put into cla.s.ses, those cla.s.ses can be admitted to be genera or species only by courtesy.

[27] In the fuller discussion which Archbishop Whately has given to this subject in his later editions, he almost ceases to regard the definitions of names and those of things as, in any important sense, distinct. He seems (9th ed. p. 145) to limit the notion of a Real Definition to one which "explains anything _more_ of the nature of the thing than is implied in the name;" (including under the word "implied,"

not only what the name connotes, but everything which can be deduced by reasoning from the attributes connoted). Even this, as he adds, is usually called, not a Definition, but a Description; and (as it seems to me) rightly so called. A Description, I conceive, can only be ranked among Definitions, when taken (as in the case of the zoological definition of man) to fulfil the true office of a Definition, by declaring the connotation given to a word in some special use, as a term of science or art: which special connotation of course would not be expressed by the proper definition of the word in its ordinary employment.

Mr. De Morgan, exactly reversing the doctrine of Archbishop Whately, understands by a Real Definition one which contains _less_ than the Nominal Definition, provided only that what it contains is sufficient for distinction. "By _real_ definition I mean such an explanation of the word, be it the whole of the meaning or only part, as will be sufficient to separate the things contained under that word from all others. Thus the following, I believe, is a complete definition of an elephant: An animal which naturally drinks by drawing the water into its nose, and then spurting it into its mouth."--_Formal Logic_, p. 36. Mr. De Morgan's general proposition and his example are at variance; for the peculiar mode of drinking of the elephant certainly forms no part of the meaning of the word elephant. It could not be said, because a person happened to be ignorant of this property, that he did not know what an elephant means.

[28] In the only attempt which, so far as I know, has been made to refute the preceding argumentation, it is maintained that in the first form of the syllogism,

A dragon is a thing which breathes flame, A dragon is a serpent, Therefore some serpent or serpents breathe flame,

"there is just as much truth in the conclusion as there is in the premises, or rather, no more in the latter than in the former. If the general name serpent includes both real and imaginary serpents, there is no falsity in the conclusion; if not, there is falsity in the minor premise."

Let us, then, try to set out the syllogism on the hypothesis that the name serpent includes imaginary serpents. We shall find that it is now necessary to alter the predicates; for it cannot be a.s.serted that an imaginary creature breathes flame: in predicating of it such a fact, we a.s.sert by the most positive implication that it is real and not imaginary. The conclusion must run thus, "Some serpent or serpents either do or are _imagined_ to breathe flame." And to prove this conclusion by the instance of dragons, the premises must be, A dragon is _imagined_ as breathing flame, A dragon is a (real or imaginary) serpent: from which it undoubtedly follows, that there are serpents which are imagined to breathe flame; but the major premise is not a definition, nor part of a definition; which is all that I am concerned to prove.

Let us now examine the other a.s.sertion--that if the word serpent stands for none but real serpents, the minor premise (a dragon is a serpent) is false. This is exactly what I have myself said of the premise, considered as a statement of fact: but it is not false as part of the definition of a dragon; and since the premises, or one of them, must be false, (the conclusion being so,) the real premise cannot be the definition, which is true, but the statement of fact, which is false.

[29] "Few people" (I have said in another place) "have reflected how great a knowledge of Things is required to enable a man to affirm that any given argument turns wholly upon words. There is, perhaps, not one of the leading terms of philosophy which is not used in almost innumerable shades of meaning, to express ideas more or less widely different from one another. Between two of these ideas a sagacious and penetrating mind will discern, as it were intuitively, an un.o.bvious link of connexion, upon which, though perhaps unable to give a logical account of it, he will found a perfectly valid argument, which his critic, not having so keen an insight into the Things, will mistake for a fallacy turning on the double meaning of a term. And the greater the genius of him who thus safely leaps over the chasm, the greater will probably be the crowing and vain-glory of the mere logician, who, hobbling after him, evinces his own superior wisdom by pausing on its brink, and giving up as desperate his proper business of bridging it over."

BOOK II.

OF REASONING.

?????s???? de t??t?? ????e? ?d?, d?? t????, ?a? p?te, ?a? p?? ???eta?

p?? s??????s?? ?ste??? d? ?e?t??? pe?? ?p?de??e??. ???te??? ??? pe??

s??????s?? ?e?t???, ? pe?? ?p?de??e??, d?? t? ?a????? ????? e??a? t??

s??????s??. ? ?? ??? ?p?de????, s??????s?? t??; ? s??????s?? d? ??

p??, ?p?de????.

ARIST. _a.n.a.lyt. Prior._ l. i. cap. 4.

CHAPTER I.

OF INFERENCE, OR REASONING, IN GENERAL.

1. In the preceding Book, we have been occupied not with the nature of Proof, but with the nature of a.s.sertion: the import conveyed by a Proposition, whether that Proposition be true or false; not the means by which to discriminate true from false Propositions. The proper subject, however, of Logic is Proof. Before we could understand what Proof is, it was necessary to understand what that is to which proof is applicable; what that is which can be a subject of belief or disbelief, of affirmation or denial; what, in short, the different kinds of Propositions a.s.sert.

This preliminary inquiry we have prosecuted to a definite result.

a.s.sertion, in the first place, relates either to the meaning of words, or to some property of the things which words signify. a.s.sertions respecting the meaning of words, among which definitions are the most important, hold a place, and an indispensable one, in philosophy; but as the meaning of words is essentially arbitrary, this cla.s.s of a.s.sertions are not susceptible of truth or falsity, nor therefore of proof or disproof. a.s.sertions respecting Things, or what may be called Real Propositions, in contradistinction to verbal ones, are of various sorts.

We have a.n.a.lysed the import of each sort, and have ascertained the nature of the things they relate to, and the nature of what they severally a.s.sert respecting those things. We found that whatever be the form of the proposition, and whatever its nominal subject or predicate, the real subject of every proposition is some one or more facts or phenomena of consciousness, or some one or more of the hidden causes or powers to which we ascribe those facts; and that what is predicated or a.s.serted, either in the affirmative or negative, of those phenomena or those powers, is always either Existence, Order in Place, Order in Time, Causation, or Resemblance. This, then, is the theory of the Import of Propositions, reduced to its ultimate elements: but there is another and a less abstruse expression for it, which, though stopping short in an earlier stage of the a.n.a.lysis, is sufficiently scientific for many of the purposes for which such a general expression is required. This expression recognises the commonly received distinction between Subject and Attribute, and gives the following as the a.n.a.lysis of the meaning of propositions:--Every Proposition a.s.serts, that some given subject does or does not possess some attribute; or that some attribute is or is not (either in all or in some portion of the subjects in which it is met with) conjoined with some other attribute.

We shall now for the present take our leave of this portion of our inquiry, and proceed to the peculiar problem of the Science of Logic, namely, how the a.s.sertions, of which we have a.n.a.lysed the import, are proved or disproved; such of them, at least, as, not being amenable to direct consciousness or intuition, are appropriate subjects of proof.

We say of a fact or statement, that it is proved, when we believe its truth by reason of some other fact or statement from which it is said to _follow_. Most of the propositions, whether affirmative or negative, universal, particular, or singular, which we believe, are not believed on their own evidence, but on the ground of something previously a.s.sented to, from which they are said to be _inferred_. To infer a proposition from a previous proposition or propositions; to give credence to it, or claim credence for it, as a conclusion from something else; is to _reason_, in the most extensive sense of the term. There is a narrower sense, in which the name reasoning is confined to the form of inference which is termed ratiocination, and of which the syllogism is the general type. The reasons for not conforming to this restricted use of the term were stated in an earlier stage of our inquiry, and additional motives will be suggested by the considerations on which we are now about to enter.

2. In proceeding to take into consideration the cases in which inferences can legitimately be drawn, we shall first mention some cases in which the inference is apparent, not real; and which require notice chiefly that they may not be confounded with cases of inference properly so called. This occurs when the proposition ostensibly inferred from another, appears on a.n.a.lysis to be merely a repet.i.tion of the same, or part of the same, a.s.sertion, which was contained in the first. All the cases mentioned in books of Logic as examples of quipollency or equivalence of propositions, are of this nature. Thus, if we were to argue, No man is incapable of reason, for every man is rational; or, All men are mortal, for no man is exempt from death; it would be plain that we were not proving the proposition, but only appealing to another mode of wording it, which may or may not be more readily comprehensible by the hearer, or better adapted to suggest the real proof, but which contains in itself no shadow of proof.

Another case is where, from an universal proposition, we affect to infer another which differs from it only in being particular: as All A is B, therefore Some A is B: No A is B, therefore Some A is not B. This, too, is not to conclude one proposition from another, but to repeat a second time something which had been a.s.serted at first; with the difference, that we do not here repeat the whole of the previous a.s.sertion, but only an indefinite part of it.

A third case is where, the antecedent having affirmed a predicate of a given subject, the consequent affirms of the same subject something already connoted by the former predicate: as, Socrates is a man, therefore Socrates is a living creature; where all that is connoted by living creature was affirmed of Socrates when he was a.s.serted to be a man. If the propositions are negative, we must invert their order, thus: Socrates is not a living creature, therefore he is not a man; for if we deny the less, the greater, which includes it, is already denied by implication. These, therefore, are not really cases of inference; and yet the trivial examples by which, in manuals of Logic, the rules of the syllogism are ill.u.s.trated, are often of this ill-chosen kind; formal demonstrations of conclusions to which whoever understands the terms used in the statement of the data, has already, and consciously, a.s.sented.

The most complex case of this sort of apparent inference is what is called the Conversion of propositions; which consists in turning the predicate into a subject, and the subject into a predicate, and framing out of the same terms thus reversed, another proposition, which must be true if the former is true. Thus, from the particular affirmative proposition, Some A is B, we may infer that Some B is A. From the universal negative, No A is B, we may conclude that No B is A. From the universal affirmative proposition, All A is B, it cannot be inferred that all B is A; though all water is liquid, it is not implied that all liquid is water; but it is implied that some liquid is so; and hence the proposition, All A is B, is legitimately convertible into Some B is A.

This process, which converts an universal proposition into a particular, is termed conversion _per accidens_. From the proposition, Some A is not B, we cannot even infer that some B is not A; though some men are not Englishmen, it does not follow that some Englishmen are not men. The only mode usually recognised of converting a particular negative proposition, is in the form, Some A is not B, therefore, something which is not B is A; and this is termed conversion by contraposition. In this case, however, the predicate and subject are not merely reversed, but one of them is changed. Instead of [A] and [B], the terms of the new proposition are [a thing which is not B], and [A]. The original proposition, Some A _is not_ B, is first changed into a proposition quipollent with it, Some A _is_ "a thing which is not B;" and the proposition, being now no longer a particular negative, but a particular affirmative, _admits_ of conversion in the first mode, or as it is called, _simple_ conversion.[1]