CLa.s.sIFICATION BY SERIES.
The object of Cla.s.sification generally is to bring our ideas of objects into the order best fitted for prosecuting inductive enquiries into the laws of the phenomena generally. But a Cla.s.sification which aims at facilitating an inductive enquiry into the laws of some special phenomenon, must be based on that phenomenon itself. The requisites of such a cla.s.sification are, first, the bringing into one cla.s.s all _kinds_ of things which exhibit the phenomenon; next, the arranging them in a _series_, according to the degrees in which they exhibit it.
Such a cla.s.sification has been largely applied in Comparative Anatomy and Physiology (and these alone), since there has been found a recognisable difference in the degree in which animals possess one main phenomenon, viz. Animal Life.
This arrangement of the instances, whence the law is to be collected, in a series, is that which is always implied in and is a condition of _any_ application of the method, viz. that of Concomitant Variations, which must be used when conjoined circ.u.mstances cannot easily be separated by experiment. But sometimes (and it is so in Zoology) the law of the subject of the special enquiry (e.g. Animal Life) has such influence over the general character of the objects, that all other differences among them seem mere modifications of it; and then the cla.s.sification required for the special purpose becomes the determining principle of the cla.s.sification of the same objects for general purposes.
To recognise the ident.i.ty of phenomena which thus differ only in degree, we must a.s.sume a type-species. This will be that _kind_ which has the cla.s.s-properties in their greatest intensity (and, therefore, most easily studied with all their effects); and we must conceive the other varieties as instances of degeneracy from that type.
The divisions of the series must be determined by the principles of _natural_ grouping in general (that is, in effect, by natural affinity); in subordination, however, to the principle of a natural series; that is, in the same group must not be placed things which ought to occupy different points of the general scale.
Zoology affords the only _complete_ example of the true principles of rational cla.s.sification, whether as to the formation of groups or of series. Yet the same principles are applicable to all cases (to art and business as well as science) where the various parts of a wide subject have to be brought into mental co-ordination.
BOOK V.
FALLACIES.
CHAPTER I.
FALLACIES IN GENERAL.
The habit of reasoning well is the only complete safeguard against reasoning ill, that is, against drawing conclusions with insufficient evidence, a practice which the various contradictory opinions, particularly about the phenomena relating to Man, show to be even now common, and that too among the most enlightened. But, to be able to explain an error is a necessary condition of seeing the truth; for, "Contrariorum eadem est Scientia." Consequently, a work on Logic must cla.s.sify Fallacies, that is, the varieties of Apparent Evidence; for they _can_ be cla.s.sified, though not in respect of their negative quality of being either not evidence at all, or inconclusive, yet in respect of the positive property they have of _appearing_ to be evidence.
As Logic has been here treated as embracing the whole reasoning process, so it must notice the fallacies incident to any part of it (not to Ratiocination merely), whether arising from faulty Induction, or from faulty Ratiocination, or from dispensing wholly with either or both of them. It does not treat of errors from negligence, or from inexpertness in using right methods, nor does it treat of errors from moral causes, viz. Indifference to truth, or Bias by our wishes or our fears; for the moral causes are but the _remote_ and _predisposing_, not the _exciting_ causes of opinions; and therefore inferences from them, since they must always involve the intellectual operation of admitting insufficient evidence as sufficient, really come under a cla.s.sification of the things which wrongly _appear_ evidence to the _understanding_.
Fallacies may be arranged, with reference either to the cause which makes them (erroneously) appear evidence, or to the particular kind of evidence they simulate. The following cla.s.sification is grounded on both these considerations jointly.
CHAPTER II.
CLa.s.sIFICATION OF FALLACIES.
The business of Logic is, not to enumerate false opinions, but to enquire what property in the facts led to them, that is, what peculiarity of relation between two facts made us suppose them habitually conjoined or disjoined, and thus regard the presence or absence of the one as evidence of that of the other. For every such property in the facts, or our mode of considering them, there is a corresponding cla.s.s of Fallacies.
As the supposed habitual connexion or repugnance of two facts may be admitted, either as a self-evident and axiomatic truth, or as itself an inference, the first great division is into Fallacies of Simple Inspection or _a priori_ Fallacies, and Fallacies, of Inference. But there is also an intermediate cla.s.s. For, sometimes an inference is erroneous through our not conceiving what our premisses precisely are, and from our therefore subst.i.tuting new premisses for the old, or a new conclusion for the one we undertook to prove; and this is called the Fallacy of Confusion. Under this head, indeed, of Fallacies of Confusion, might strictly be brought almost any fallacy, though falling also under some other head: for, some of the links in an argument, especially if sophistical, are sure to be suppressed; and, it being left doubtful which is the proposition to be supplied, we can seldom tell with certainty under _which_ cla.s.s the fallacy absolutely comes. It is, however, convenient to reserve the name _Fallacy of Confusion_ for cases where Confusion is the _sole_ cause of the error.
Cases, then, where there is more or less ground for the error in _the nature of the apparent evidence itself_, the evidence being a.s.sumed to be of a certain sort, and a false conclusion being drawn from it, may be cla.s.sed as Fallacies of Inference. According as the apparent evidence consists of particular facts, or of foregone generalisations, we call the errors Fallacies of Induction or of Deduction. Each of these cla.s.ses, again, may be subdivided into two species, according as the apparent evidence is either false, or, though true, inconclusive. Such subdivisions of the Fallacy of Induction are respectively called, in the former case, Fallacies of Observation (including cases where the facts are not directly observed, but inferred), and, in the latter, Fallacies of Generalisation. Among Fallacies of Deduction, those which proceed on false premisses have no specific name, for they must fall under one of the other heads of Fallacies; but those, the premisses of which, though true, do not support the conclusion, compose a subdivision, which may be specified as Fallacies of Ratiocination.
CHAPTER III.
FALLACIES OF SIMPLE INSPECTION; OR, a PRIORI FALLACIES.
There must be some _a priori_ knowledge, some propositions to be received without proof; for there cannot be a chain suspended from nothing. What these are is disputed, one school recognising as ultimate premisses only the facts of our subjective consciousness, e.g.
Sensations, while Ontologists hold that the mind intuitively, and not through experience, recognises as realities other existences, e.g.
Substances, which are suggested by, though not inferrible from, those facts of consciousness. But, as both schools, in fact, allow that the mind infers the _reality_ from the _idea_ of a thing, and that it may do this unduly, there results a cla.s.s of Fallacies resting on the tacit a.s.sumption that the objects in nature have the same order as our ideas of them. Hence not only arose the vulgar belief that facts which make us think of an event are omens foreboding (e.g. lucky or unlucky names), or even causing its occurrence; but even men of science both did and do fall into this Fallacy. The following dogmas express the different forms of this error:--
1. [Greek: a]. _Things which we cannot help thinking of together must coexist_; thus Descartes held that, because existence is involved (though really only by the thinker himself) in the idea of a geometrical figure, a thing like the idea must exist. [Greek: b]. _Whatever is inconceivable is false._ The latter proposition has been defended by drawing a distinction between the principle, and its possibly wrong application to facts, e.g. to Antipodes; but how can we ever know that it has been rightly applied? Coleridge, again, has distinguished between the unimaginable, which he thinks may possibly be true, and the inconceivable, which he thinks cannot be; but Antipodes were imaginable at the same period when they were inconceivable. In fact, as even to Newton it seemed inconceivable, that a thing should act where it is not (e.g. that the sun should act upon the earth without the medium of an ether), simply because his mind was not familiar with the idea, so it _may_ be with _our_ incapability (if not, indeed, resulting merely from our limited faculties) of _conceiving_, e.g. that matter cannot think; that s.p.a.ce is infinite; that _ex nihilo nihil fit_. Leibnitz"s tenet that all _natural_ phenomena must be explicable _a priori_, and the further a.s.sumption by some that Nature always acts by the simplest, i.e.
by the most easily conceivable means (and that, therefore, e.g. the heavenly bodies have a circular movement), exhibit vividly this Fallacy of Simple Inspection.
2. _Whatever can be thought of apart, or has a separate name, exists apart as a separate ent.i.ty_, e.g. Nature, Time, qualities, as e.g.
Whiteness, and, worst of all, the Substantiae Secundae. Mysticism is this habit of ascribing objective existence to the subjective creations of the mind, and reasoning from them to the things themselves.
3. _A fact must follow a certain law, because we see no reason for its deviating from it in one way rather than in another._ This, which is the same as the Principle of the Sufficient Reason, has been used to prove the Law of Inertia (the very point to be proved, viz. that only external force can be a sufficient reason for motion _in a particular direction_, being a.s.sumed), and also the First Law of Motion, the argument being, in the latter case, that a moving body, if it do _not_ continue of itself to move uniformly in a straight line, must deviate right or left, and that there is _no reason_ for its going one way more than the other: to which the answer is, that, apart from experience, we could not know whether or not there were a reason. Geometers often fall into this Fallacy.
4. _The differences in nature must correspond to our received distinctions_ (in names and cla.s.sifications). Thus, the Greeks thought that, by determining the meanings of words, they ascertained facts.
Aristotle usually starts with "We say thus or thus." So, with the _Doctrine of Contrarieties_, in which the Pythagoreans and others a.s.sumed that oppositions in language imply similar ones in nature.
Hence, too, the ancient belief in the essential difference between the laws of things terrestrial and things celestial, and in man"s incapability of imitating nature"s works. Bacon"s error (which vitiates his inductive system) was a.n.a.logous, in looking (either through his eagerness for practical results, or a lingering belief that causes were the sole object of philosophy) for the cause of given effects rather than the effects of a given cause. Hence sprang his tacit a.s.sumption (and that in enquiries into the causes of a thing"s sensible qualities, where it was especially fatal), that in all cases, e.g. of heat or cold, the _forma_, or set of conditions, is _one_ thing. A similar notion, viz. that each property of gold, as of other things, has its one _forma_, produced the belief in Alchemy.
5. The conditions of a phenomenon often do resemble the phenomenon itself, e.g. in cases of Motion, Contagion, Feelings; but it is a Fallacy to suppose that _they must or probably will_. By this fancied law men guided their conjectures. Thus, the _Doctrine of Signatures_ was, that substances showed their uses as medicines by external resemblance, either to their supposed effect, or to the disease. So, the Cartesians, and even Leibnitz, argued, that nothing physical but previous motion could account for motion, explaining the human body"s voluntary motions by Nervous Vibrations or by Animal Spirits. Hence, too, the inference that there is a correspondence between the physical qualities of the cause, and like or like-named ones, either of the phenomenon (e.g. between sharp particles and a sharp taste), or of its effects (e.g. between the redness of Mars, and fire and slaughter as results of that planet"s influence). In metaphysics, the Epicureans"
doctrine of _species sensibiles_, and the moderns" of _perception through ideas_, arose from this fallacy (combined with another, viz.
that a thing cannot act where it is not). Again, the conditions of a thing are sometimes spoken of even as though they were the thing itself.
Thus, in the Novum Organon, heat (i.e. really the conditions of the feeling of it) is called a kind of motion; and Darwin, in his Zoonomia, after describing _idea_ as a kind of _notion of external things_, defines it as _a motion of the fibres_. Cousin says: "Tout ce qui est vrai de l"effet est vrai de la cause," though, the reverse _might_ be true; and Coleridge affirms, as _an evident truth_, that mind and matter, as having no common property, cannot act on each other. The same fallacy led Leibnitz to his _pre-established harmony_, and Malebranche to his _occasional causes_. So, Cicero argues that mental pleasures, if arising from the bodily, could not, as they do, exceed their cause; and Descartes, that the Efficient Cause must have all the perfections of the effect. Conversely Descartes, too, and persons who a.s.sail, e.g. the Principle of Population by reference to Divine benevolence (thus implying that, because G.o.d is perfect, therefore what _they_ think perfection must obtain in nature), a.s.sume that effects must resemble their causes.
CHAPTER IV.
FALLACIES OF OBSERVATION.
A fallacy of Observation (the first of the three fallacies of Proof) may be either negative or positive.
1. The former, which is called Non-observation, is a case, not of a positive mis-estimate of evidence, or of the proper faculties (whether the senses or reason) not having been employed, but simply of the non-employment of any of the faculties. It arises ([Greek: a]) from neglect of instances. Sometimes this is when there is a stronger motive to remember the instances on the one side, and the observers have neglected the principle of the Elimination of Chance. Hence (the mind, as Bacon says, being more moved by affirmative than by negative instances) the belief in predictions, e.g. about the weather, because they occasionally turn out correct; and the credit of the proverb, that "Fortune favours fools," since the cases of a wise man"s success through luck are forgotten in his more numerous successes through genius. But a preconceived opinion is the _chief_ cause why opposing instances are overlooked. Hence originate the errors about physical facts (e.g. of Copernicus"s foes, and friends, too, about the falling stone), and _a fortiori_, on moral, social, and religious subjects, where yet stronger feelings are involved.
The fallacy of Non-observation may occur ([Greek: b]) from neglect, not of the material instances wholly, but of some material facts in them, e.g. in cases of cures by quack remedies (such as Kenelm Digby"s "sympathetic powder"), of some attendant fact (as exclusion of air from a wound, rest, regimen, and the like) which really worked the cure.
Sometimes the neglected fact is one ascertainable, not by the senses, but by reasoning, which has been overlooked. Thus, Cousin"s argument that, if the sole end of punishment were to prevent crime by intimidating intending criminals, the punishment of the innocent, indiscriminately with the guilty, would have the same effect, ignores the fact that the innocent would then be equally intimidated, and so the punishment would be of no use as an example to criminals. So, in Political Economy, where the effects of a cause often consist of two sets of phenomena, the one obvious, the other deeper under the surface, and exactly contrary, the latter is often neglected. This was why the rapidly spent capital of the prodigal was supposed formerly to employ more labour than the invested savings of the parsimonious, and the purchase of native goods to encourage native industry more than the purchase of foreign.
2. The error in Mal-observation, which is the _positive_ kind of Mis-observation, is not the overlooking facts, but the seeing them wrong. It arises from mistaking what is in fact inference (as much _must_ be, whenever we try to observe or to describe) for perception, which is infallible evidence of what is really perceived. The Anti-Copernicans, when they appealed to common sense, made this mistake.
So do untrained persons generally in describing facts, especially natural phenomena (e.g. apothecaries and nurses in stating symptoms), and that, too, in proportion to their ignorance. We might expect this, since usually the actual perceptions of the senses (e.g. the colour and extension) are not of interest, except as marks whence to draw inferences about something else (e.g. about the body, to which these qualities belong). Painters, therefore, to know what the sensation actually was, have to go through a special training. But this confusion of inference with perception is still more likely in highly abstract subjects; and, consequently, in these, mere, and often false inferences, have continually been regarded as intuitive judgments.