Aristotle
proposition which contradicts it in appearance only but not in
reality, because he does not know what are the true and sufficient
conditions of a valid Elenchus. In order to be valid, it must be
real, not merely verbal; it must be proved by good syllogistic
premisses, without any _Petitio Principii_; and it must deny the same
matter, in the same relations, and at the same time, as that which
the thesis affirmed. Thus, it is no contradiction to affirm and deny
doubleness of the same body; both affirmation and denial may be true,
if you take the comparison against different numbers or different
bodies, or at different times. Sometimes persons neglect some of
these conditions, and fancy that they have contradicted the thesis,
when they have not: this is _Ignoratio Elenchi_.[32] (If the thesis
be an affirmative universal, it _is_ sufficient contradiction if you
prove a negative particular against it.)
[Footnote 32: Soph. El. v. p. 167, a. 21-35: [Greek: oi( de\ para\
to\ mê\ diôri/sthai ti/ e)sti sullogismo\s ê)\ ti/ e)/legchos, a)lla\
para\ tê\n e)/lleipsin gi/nontai tou= lo/gou.]
We may remark, by the way, that it is not very consistent in
Aristotle to recognize one general head of Sophistical Refutation
called _Ignoratio Elenchi_, after the definition that he has given of
the Sophist at the beginning of this treatise. He had told us that
the Sophist was a dishonest man, who made it his profession to study
and practise these tricks, for the purpose of making himself pass for
a clever man, and of getting money. According to this definition,
there is no _Ignoratio Elenchi_ in the Sophist, though there may be
in the person who supposes himself refuted. The Sophist is assumed to
know what he is about, and to be aware that his argument is a
fallacious one.]
4. The fourth head includes what are called _Fallaciæ Consequentis_:
when a man inverts the relation between predicate and subject in a
categorical proposition affirmative and universal, thinking that it
may be simply converted or that the subject may be truly affirmed of
the predicate; or when, in an hypothetical proposition, he inverts
the relation between antecedent and consequent, arguing that, because
the consequent is true, the antecedent must for that reason be true
also. Honey is of yellow colour; you see a yellow substance, and you
infer for that reason that it must be honey. Thieves generally walk
out by night; you find a man walking out by night, and you infer that
he must be a thief. These are inferences from Signs, opinions founded
on facts of sense, such as are usually employed in Rhetoric; often or
usually true, but not necessarily or universally true, and therefore
fallacious when used as premisses in a syllogism.[33]
[Footnote 33: Soph. El. v. p. 167, b. 1-18. This head (_Fallacia
Consequentis_) is not essentially distinguishable from the first
(_Fallacia Accidentis_), being nothing more than a peculiar species
or variety thereof, as Aristotle himself admits a little farther
on--vi. p. 168, a. 26; vii. p. 169, b. 7; viii. p. 170, a. 3. Compare
also xxviii. p. 181, a. 25.]
5. The fifth head is that of _Petitio Principii_: a man sometimes
assumes for his premiss what is identical with the conclusion to be
proved, without being aware of the identity.[34]
[Footnote 34: Ibid. v. p. 167, a. 38: [Greek: dia\ to\ mê\ du/nasthai
sunora=n to\ tau)to\n kai\ to\ e(/teron].]
6. The sixth head of Fallacy--_Non Causa pro Causâ_--is, when we
mistake for a cause that which is not really a cause; or, to drop the
misleading word _cause_, and to adopt the clearer terms in which this
same fallacy is announced in the Analytica Priora[35]--_Non per
Hoc_--_Non propter Hoc_, it arises when we put forward, as an essential
premiss of a given conclusion, something that is not really an
essential premiss thereof. When you intend to refute a given thesis
by showing, that, if admitted, it leads to impossible or absurd
conclusions, you must enunciate that thesis itself among the
premisses that lead to such absurdities.[36] But, though enunciated
in this place, it may often happen that the thesis may be an
unnecessary adjunct--not among the premisses really pertinent and
essential: and that the impossible conclusion may be sufficiently
proved, even though the thesis were omitted. Still, since the thesis
is declared along with the rest, it will appear falsely to be a part
of the real proof. It will often appear so even to yourself the
questioner; you not detecting the fallacy.[37] Under such
circumstances the respondent meets you by _Non propter Hoc_. He
admits your conclusion to be impossible, and at the same time to be
duly proved, but he shows you that it is proved by evidence
independent of his thesis, and not by reason or means of his thesis.
Accordingly you have advanced a syllogism good in itself, but not
good for the purpose which you aimed at;[38] viz., to refute the
thesis by establishing that it led to impossible consequences. You
will fail, even if the impossible consequence which you advance is a
proposition conjoined with the thesis through a continuous series of
intermediate propositions, each of them having one common term with
the next. Much more will you fail, if your impossible consequence is
quite foreign and unconnected with the thesis; as we sometimes find
in Dialectic.
[Footnote 35: Ibid. b. 21; vii. p. 169, b. 13. Compare Analyt. Prior.
II. xvii. p. 65.
In commenting on the above chapter of the Analytica Priora, I have
already remarked (Vol. I. p. 258, note) how much better is the
designation there given of the present fallacy--_Non per Hoc_
([Greek: ou) para\ tê\n the/sin to\ pseu=dos])--than the designation
here given of the same fallacy--_Non Causa pro Causâ_. Aristotle is
speaking of a syllogistic process, consisting of premisses and a
conclusion; the premisses being the _reasons_ or grounds of the
conclusion, not the _cause_ thereof, as that term is commonly
understood. The term _cause_ is one used in so many different senses
that we cannot be too careful in reasoning upon it. See Whately's
remarks on this subject, Bk. iii. Sect. 14, of his Logic: also his
Appendix I. to that work, under article _Reason_.]
[Footnote 36: Soph. El. v. p. 167, b. 24: [Greek: e)a\n ou)=n
e)gkatarithmê/thê| e)n toi=s a)nagkai/ois e)rôtê/masi pro\s to\
sumbai=non a)du/naton, do/xei para\ tou=to gi/nesthai polla/kis o(
e)/legchos.]]
[Footnote 37: Ibid. b. 35: [Greek: kai\ lantha/nei polla/kis ou)ch
ê(=tton au)tou\s tou\s e)rôtô=ntas to\ toiou=ton.]]
[Footnote 38: Ibid. b. 34: [Greek: a)sullo/gistoi me\n ou)=n a(plô=s
ou)k ei)si\n oi( toiou=toi lo/goi, pro\s de\ to\ prokei/menon
a)sullo/gistoi.]]
7. The seventh and last of these heads of Fallacy is, when the
questioner puts two distinct questions in the same form of words, as
if they were one--_Fallacia Plurium Interrogationum ut Unius_. In
well-conducted Dialectic the respondent was assumed to reply either
Yes or No to the question put; or, if it was put in the form of an
alternative, he accepted distinctly one term of the alternative.
Under such conditions he could not reply to one of these
double-termed questions without speaking falsely or committing himself.
Are the earth and the sea liquid? Is the heaven or the earth sea? The
questions are improperly put, and neither admits of any one correct
answer. You ought to confine yourself to one question at a time, with
one subject and one predicate, making what is properly understood by
one single proposition. The two questions here stated as examples
ought properly to be put as four.[39]
[Footnote 39: Ibid. b. 38-p. 168, a. 16; vi. p. 169, a. 6-12. [Greek:
ê( ga\r pro/tasi/s e)stin e(\n kath' e(no/s.--ei) ou)=n mi/a
pro/tasis ê( e(\n kath' e(no\s a)xiou=sa, kai\ a(plô=s e)/stai
pro/tasis ê( toiau/tê e)rô/têsis.]
The examples given of this fallacy by Aristotle are so palpable--the
expounder of every fallacy _must_ make it clear by giving examples
that every one sees through at once--that we are tempted to imagine
that no one can be imposed on by it. But Aristotle himself remarks,
very justly, that there occur many cases in which we do not readily
see whether one question only, or more than one, is involved; and in
which one answer is made, though two questions are concerned. To set
out distinctly all the separate debateable points is one of the most
essential precautions for ensuring correct decision. The importance
of such discriminating separation is one of the four rules prescribed
by Descartes in his Discours de la Méthode. The present case comes
under Mr. Mill's Fallacies of Confusion.]
Aristotle has thus distinguished and classified Fallacies under
thirteen distinct heads in all--six _In Dictione_, and seven _Extra
Dictionem_; among which last one is _Ignoratio Elenchi_. He now
proceeds to show that, in another way of looking at the matter, all
the Fallacies ranged under the thirteen heads, may be shown to be
reducible to this single one--_Ignoratio Elenchi_. Every Fallacy,
whatever it be, transgresses or fails to satisfy, in some way or
other, the canons or conditions which go to constitute a valid
Elenchus,[40] or a valid Syllogism. For a true Elenchus is only one
mode of a true Syllogism; namely, that of which the conclusion is
contradictory to some given thesis or proposition.[41] With this
particular added, the definition of a valid Syllogism will also be
the definition of a good Elenchus. And thus _Ignoratio
Elenchi_--misconception or neglect of the conditions of a good
Elenchus--understood in its largest meaning, is rather a
characteristic common to all varieties of Fallacy, than one variety
among others.[42]
[Footnote 40: Soph. El. vi. p. 168, a. 19: [Greek: e)/sti ga\r
a(/pantas a)nalu=sai tou\s lechthe/ntas tro/pous ei)s to\n tou=
e)le/gchou diorismo/n.]]
[Footnote 41: Ibid. a. 35.]
[Footnote 42: Ibid. p. 169, b. 15.]
In regard to two among the thirteen heads--_Fallacia Accidentis_ and
_Fallacia Consequentis_ (which however ought properly to rank as only
one head, since the second is merely a particular variety of the
first)--Aristotle's observations are remarkable. After having pointed
out that a Syllogism embodying this fallacy will not be valid or
conclusive (thus showing that it involves _Ignoratio Elenchi_), he
affirms that even scientific men were often not aware of it, and
conceived themselves to be really refuted by an unscientific opponent
urging against them such an inconclusive syllogism. To take an
example:--Every triangle has its three angles equal to two right
angles; every triangle is a figure; therefore, every figure has its
three angles equal to two right angles.[43] Here we have an invalid
syllogism; for it is in the Third figure, and sins against the
conditions of that figure, by exhibiting an universal affirmative
conclusion: it is a syllogism properly concluding in _Darapti_, but
with conclusion improperly generalized. Yet Aristotle intimates that
a scientific geometer of his day, in argument with an unscientific
opponent, would admit the conclusion to be well proved, not knowing
how to point out where the fallacy lay: he would, if asked, grant the
premisses necessary for constructing such a syllogism; and, even if
not asked, would suppose that he had already granted them, or that
they ought to be granted.[44]
[Footnote 43: Ibid. p. 168, a. 40: [Greek: ou)d' ei) to\ tri/gônon
duoi=n o)rthai=n i)/sas e)/chei, _sumbe/bêke d' au)tô=| schê/mati
ei)=nai_ ê)\ prô/tô| ê)\ a)rchê=|, o(/ti _schê=ma_ ê)\ a)rchê\ ê)\
prô=ton tou=to.]
Here we have Figure reckoned as an _accident_ of Triangle. This is a
specimen of Aristotle's occasional laxity in employing the word
[Greek: sumbebêko/s]. He commonly uses it as contrasted with