Aristotle
into _Petitio Principii_, Aristotle contends that you can demonstrate
it in the way of refutation,[22] relatively to a given opponent,
provided such opponent will not content himself with simply denying
it, but will besides advance some affirmative thesis of his own, as a
truth in which he believes; or provided he will even grant the fixed
meaning of words, defining them in a manner significant alike to
himself and to others,--each word to have either one fixed meaning,
or a limited number of different meanings, clear and well
defined.[23] It is impossible for two persons to converse, unless
each understands the other. A word which conveys to the mind not one
meaning, but a multitude of unconnected meanings, is for all useful
purposes unmeaning.[24] If, therefore, the opponent once binds
himself to an affirmative definition of any word, this definition may
be truly predicated of the _definitum_ as subject; while he must be
considered as interdicting himself from predicating of the same
subject the negative of that definition. But when you ask for the
definition, your opponent must answer the question directly and _bonâ
fide_. He must not enlarge his definition so as to include both the
affirmative and negative of the same proposition; nor must he tack on
to the real essence (declared in the definition) a multitude of
unessential attributes. If he answers in this confused and perplexing
manner, he must be treated as not answering at all, and as rendering
philosophical discussion impossible.[25] Such a mode of speaking goes
to disallow any ultimate essence or determinate subject, and shuts
out all predication; for there cannot be an infinite regress of
predicates upon predicates, and accidents upon accidents, without
arriving at an ultimate substratum--Subject or Essence.[26] If,
wherever you can truly affirm a predicate of any subject, you can
also truly deny the same predicate of the same subject, it is
manifest that all subjects are one: there is nothing to discriminate
man, horse, ship, wall, &c., from each other; every one speaks truth,
and every one at the same time speaks falsehood; a man believes and
disbelieves the same thing at the same time; or he neither believes
nor disbelieves, and then his mind is blank, like a vegetable.[27]
[Footnote 20: Aristot. Metaph. [Greek: G]. iii. p. 1005, b. 26; K. v.
p. 1062, a. 32. Here Aristotle intimates that Herakleitus may have
asserted what he did not believe; though we find him in another place
citing Herakleitus as an example of those who adhered as obstinately
to their opinions as other persons adhered to demonstrated truth
(Ethic. Nik. VII. v. p. 1146, b. 30.).]
[Footnote 21: Aristot. Metaph. [Greek: G]. iv. p. 1006, a. 5: [Greek:
a)xiou=si dê\ kai\ tou=to a)podeiknu/nai tine\s di' a)paideusi/an;
e)/sti ga\r a)paideusi/a to\ mê\ gignô/skein ti/nôn dei= zêtei=n
a)po/deixin kai\ ti/nôn ou) dei=.]]
[Footnote 22: Aristot. Metaph. [Greek: G]. iv. p. 1006, a. 11:
[Greek: e)/sti d' a)podei=xai e)legktikô=s kai\ peri\ tou/tou o(/ti
a)du/naton, a)\n mo/non ti le/gê| o( a)mphisbêtô=n.]--K. v. p. 1062,
a. 2: [Greek: kai\ peri\ tô=n toiou/tôn a(plô=s me\n ou)k e)/stin
a)po/deixis, pro\s to/nde d' e)/stin.]--p. 1062, a. 30.]
[Footnote 23: Ibid. Metaph. [Greek: G]. iv. p. 1006, a. 18-34.
[Greek: diaphe/rei d' ou)the\n ou)/d' ei) plei/ô tis phaiê/
sêmai/nein, mo/non de\ ô(risme/na.]--K. v. p. 1062, a. 12.]
[Footnote 24: Ibid. [Greek: G]. iv. p. 1006, b. 7: [Greek: to\ ga\r
mê\ e(/n ti sêmai/nein ou)the\n sêmai/nein e)sti/n, mê\ sêmaino/ntôn
de\ tô=n o)noma/tôn a)nê/|rêtai to\ diale/gesthai pro\s a)llê/lous,
kata\ de\ tê\n a)lê/theian kai\ pro\s au(to/n; ou)the\n **ga\r
e)nde/chetai noei=n mê\ noou=nta e(/n.]--K. v. p. 1062, a. 20.]
[Footnote 25: Ibid. [Greek: G]. iv. p. 1006, b. 30-p. 1007, a. 20.
[Greek: sumbai/nei to\ lechthe/n, a)\n a)pokri/nêtai to\
e)rôtô/menon. e)a\n de\ prostithê=| e)rôtô=ntos a(plô=s kai\ ta\s
a)popha/seis, ou)k a)pokri/netai to\ e)rôtô/menon.--e)a\n de\
tou=to poiê=|, ou) diale/getai.]]
[Footnote 26: Ibid. p. 1007, a. 20-b. 19: [Greek: o(/lôs d'
a)nairou=sin oi( tou=to le/gontes ou)si/an kai\ to\ ti/ ê)=n
ei)=nai.--ei) de\ pa/nta kata\ sumbebêko\s le/getai, ou)the\n e)/stai
prô=ton to\ kath' ou(=, ei) a)ei\ to\ sumbebêko\s kath'
u(pokeime/nou tino\s sêmai/nei tê\n katêgori/an; a)na/gkê a)/ra ei)s
a)/peiron i)e/nai; a)ll' a)du/naton.]]
[Footnote 27: Aristot. Met. [Greek: G]. iv. p. 1008, a. 18-b. 12:
[Greek: ei) de\ o(moi/ôs kai\ o(/sa a)pophê=sai pha/nai
a)na/gkê--pa/nta d' a)\n ei)/ê e(/n--ou)the\n dioi/sei e(/teron
e(te/rou--ei) de\ mêthe\n u(polamba/nei a)ll' o(moi/ôs oi)/etai kai\
ou)k oi)/etai, ti/ a)\n diaphero/ntôs e)/choi tô=n phutô=n?] K. v. p.
1062, a. 28.]
The man who professes this doctrine, however (continues
Aristotle[28]), shows plainly by his conduct that his mind is not
thus blank; that**, in respect of the contradictory alternative, he
does not believe either both sides or neither side, but believes one
and disbelieves the other. When he feels hungry, and seeks what he
knows to be palatable and wholesome, he avoids what he knows to be
nasty and poisonous. He knows what is to be found in the
market-place, and goes there to get it; he keeps clear of falling into
a well or walking into the sea; he does not mistake a horse for a man.
He may often find himself mistaken; but he shows by his conduct that
he believes certain subjects to possess certain definite attributes,
and not to possess others. Though we do not reach infallible truth,
we obtain an approach to it, sometimes nearer, sometimes more remote;
and we thus escape the extreme doctrine which forbids all definite
affirmation.[29]
[Footnote 28: Ibid. [Greek: G]. iv. p. 1008, b. 12-31; K. vi. p.
1063, a. 30.]
[Footnote 29: Ibid. [Greek: G]. iv. p. 1008, b. 36: [Greek: ei) ou)=n
to\ ma=llon e)ggu/teron, ei)/ê ge a)/n ti a)lêthe\s ou(= e)ggu/teron
to\ ma=llon a)lêthe/s; ka)\n ei) mê/ e)stin, a)ll' ê)/dê ge/ ti
e)sti\ bebaio/teron kai\ a)lêthinô/teron, kai\ tou= lo/gou
a)pêllagme/noi a)\n ei)/êmen tou= a)kra/tou kai\ kôlu/onto/s ti tê=|
dianoi/a| o(ri/sai.]]
It is in this manner that Aristotle, vindicating the Maxims of
Contradiction and of Excluded Middle as the highest _principia_ of
syllogistic reasoning, disposes of the two contemporaneous dogmas
that were most directly incompatible with these Maxims:--(1) The
dogma of Herakleitus, who denied all duration or permanence of
subject, recognizing nothing but perpetual process, flux, or change,
each successive moment of which involved destruction and generation
implicated with each other: _Is_ and _is not_ are both alike and
conjointly true, while neither is true separately, to the exclusion
of the other;[30] (2) The dogma of Anaxagoras, who did not deny
fixity or permanence of subject, but held that everything was mixed
up with everything; that every subject had an infinite assemblage of
contrary predicates, so that neither of them could be separately
affirmed or separately denied: The truth lies in a third alternative
or middle, between affirmation and denial.[31]
[Footnote 30: Aristot. Met. A. vi. p. 987, a. 34; [Greek: G]. v. p.
1010, a. 12: [Greek: Kra/tulos--o(\s to\ teleutai=on ou)the\n ô/|eto
dei=n le/gein a)lla\ to\n da/ktulon e)ki/nei mo/non, kai\
Ê(raklei/tô| e)peti/ma ei)po/nti o(/ti di\s tô=| au)tô=| pota/mô| ou)k
e)/stin e)mbê=nai; au)to\s ga\r ô)/|eto ou)/d' a(pa/x.] Herakleitus
adopted as his one _fundamentum_ Fire or Heat, as being the principle
of mobility or change: [Greek: chrô=ntai ga\r ô(s kinêtikê\n
e)/chonti tô=| puri\ tê\n phu/sin]--Metaph. A. iii. p. 984, b. 5.
Ibid. K. v. p. 1062, a. 31-b. 10; K. x. p. 1067, a. 5; M. iv. p.
1078, b. 15.]
[Footnote 31: Aristot. Met. K. vi. p. 1063, b. 25; A. viii. p. 989,
a. 31-b. 16. [Greek: o(/te ga\r ou)the\n ê)=n a)pokekrime/non, dê=lon
ô(s ou)the\n ê)=n a)lêthe\s ei)pei=n kata\ tê=s ou)si/as e)kei/nês,
le/gô d' oi(=on o(/ti ou)/te leuko\n ou)/te me/lan ê)\ phaio\n ê)\
a)/llo chrô=ma, a)ll' a)/chrôn ê)=n e)x a)na/gkês; o(moi/ôs de\
kai\ a)/chumon tô=| au)tô=| lo/gô| tou/tô|, ou)de\ a)/llo tô=n
o(moi/ôn ou)the/n; ou)/te ga\r poio/n ti oi(=o/n te au)to\ ei)=nai
ou)/te poso\n ou)/te ti/.]--[Greek: G]. iv. b. 1007, b. 25: [Greek:
kai\ gi/gnetai dê\ to\ tou= A)naxago/rou, o(mou= pa/nta chrê/mata;
ô(/ste mêthe\n a)lêthô=s u(pa/rchein.]--[Greek: G]. viii. p. 1012,
a. 24: [Greek: e)/oike d' o( me\n Ê(raklei/tou lo/gos, le/gôn pa/nta
ei)=nai kai\ mê\ ei)=nai, a(/panta a)lêthê= poiei=n, o( d'
A)naxago/rou ei)=nai/ ti metaxu\ tê=s a)ntipha/seôs, ô(/ste pa/nta
pseudê=; o(/tan ga\r michthê=|, ou)/t' a)gatho\n ou)/t' ou)k
a)gatho\n to\ mi=gma, ô(/st' ou)the\n ei)pei=n a)lêthe/s.]]
Having thus refuted these dogmas to his own satisfaction, Aristotle
proceeds to impugn a third doctrine which he declares to be analogous
to these two and to be equally in conflict with the two syllogistic
_principia_ which he is undertaking to vindicate. This third doctrine
is the "_Homo Mensura_" of Protagoras: Man is the measure of all
things--the measure of things existent as well as of things
non-existent: To each individual that is true or false which he
believes to be such, and for as long as he believes it. Aristotle
contends that this doctrine is homogeneous with those of Herakleitus
and Anaxagoras, and must stand or fall along with them; all three being
alike adverse to the Maxim of Contradiction.[32] Herein he follows
partially the example of Plato, who (in his Theætêtus[33]), though
not formally enunciating the Maxim of Contradiction, had declared the
tenets of Protagoras to be coincident with or analogous to those of
Herakleitus, and had impugned both one and the other by the same line
of arguments. Protagoras agreed with Herakleitus (so Plato and
Aristotle tell us) in declaring both affirmative and negative (in the
contradictory alternative) to be at once and alike true; for he
maintained that what any person believed was true, and that what any
person disbelieved was false. Accordingly, since opinions altogether
opposite and contradictory are held by different persons or by the
same person at different times, both the affirmative and the negative
of every _Antiphasis_ must be held as true alike;[34] in other words,
all affirmations and all negations were at once true and false. Such
co-existence or implication of contradictions is the main doctrine of
Herakleitus.
[Footnote 32: Aristot. Met [Greek: G]. v. p. 1009, a. 6: [Greek:
e)/sti d' a)po\ tê=s au)tê=s do/xês kai\ o( Prôtago/rou lo/gos, kai\
a)na/gkê o(moi/ôs a)/mphô au)tou\s ê)\ ei)=nai ê)\ mê\ ei)=nai.]]
[Footnote 33: Aristotle refers here to Plato by name, Metaphys.
[Greek: G]. v. p. 1010, b. 12.]
[Footnote 34: Ibid. p. 1009, a. 8-20. [Greek: a)na/gkê pa/nta a(/ma
a)lêthê= kai\ pseudê= ei)=nai.]--p. 1011, a. 30.]
I have already in another work,[35] while analysing the Platonic
dialogues Theætêtus and Kratylus, criticized at some length the
doctrine here laid down by Plato and Aristotle. I have endeavoured to
show that the capital tenet of Protagoras is essentially distinct
from the other tenets with which these two philosophers would
identify it: distinct both from the dogma of Herakleitus, That
everything is in unceasing flux and process, each particular moment
thereof being an implication of contradictions both alike true; and
distinct also from the other dogma held by others, That all cognition
is sensible perception. The Protagorean tenet "_Homo Mensura_" is
something essentially distinct from either of these two; though
possibly Protagoras himself may have held the second of the two,
besides his own. His tenet is nothing more than a clear and general
declaration of the principle of universal Relativity. True belief and