3. There were two main attacks on skepticism in
antiquity: (1) it makes action impossible; and (2) it is
self-contradictory. The first rests on the observation
that action presupposes decision, and decision involves
a choice between alternatives. Anyone who says of
things that they are “no more this than that” thereby
destroys the ground for practical decisions and so
makes action impossible. As Aristotle said (Metaphysics
1008b 26-27), “All men make unqualified judgments,
if not about all things, still about what is better and
worse” (trans. Ross). To this charge the skeptics gave
a number of answers. First of all, they pointed out that
practical decisions are made in terms of appearances.
Men naturally seek what appears good and avoid what
appears bad; in this sense they follow nature as their
guide. Skepticism does not challenge appearances, but
only the dogmatists' claim to have certain knowledge
about the nonapparent (cf. Ac. II.103; PH I.19-20).
There is therefore no conflict between skepticism and
practical decisions. The view that we live by appear-
ances is attributed by Aenesidemus to Pyrrho himself
(cf. DL IX.106), and it is implied by the fragment of
Timon already quoted, “Appearance prevails wherever
it goes.” It receives explicit statement also in the Aca-
demic tradition (cf. Plutarch, Moralia 1122) and is
accepted by Sextus (AM VII.30; PH I.21-24). Indeed,
Sextus regards the observation of appearances as the
basis of the practical arts (AM V.1-2) and of the
admonitive sign (PH II.100; AM VIII.152, 156-57).
One is reminded of Plato's description of the skill in
observing, remembering, and predicting that was
held in honor by the inhabitants of the cave (Republic
516C-D).
The skeptics also accepted tradition and custom as
a guide to action (PH I.17, 231; DL IX.61, 108; PE
XIV.18.20). Custom may be observed on the level of
appearance and followed without intellectual commit-
ment. It is on this basis, for instance, that the skeptic
performs acts of piety and avoids impiety (cf. PH
I.23-24, III.2; AM IX.49). Thus Cotta, the Academic
spokesman in Cicero's De natura deorum, insists that
he may be a philosophical skeptic and still participate
in the traditional Roman religion (ND III.5, 9). It is
not unlikely that skepticism helped to strengthen the
trend toward traditionalism in the Greco-Roman world.
Arcesilaus advanced still another guide to practical
action. According to Sextus (AM VII.158), he held that
happiness is secured through practical wisdom, practi-
cal wisdom consists in right action, and right action
is action for which a reasonable defense can be given.
The reasonable (eulogon) is thus the guide. There is
no mention of this view in the extant portions of
Cicero's Academica, but perhaps it is not mere coinci-
dence that several letters which Cicero wrote during
the period when he was working on the Academica
(June-July, 45 B.C.) contain the Greek word eulogon
or eulogia (Letters to Atticus, XIII.5, 6, 7, 22). In the
last of these (22) the reference is to a decision that
Cicero must himself make. Another letter to Atticus
(XIV.22), written a year later, uses eulogon in the
context of making conjectures about the future. Atticus
would surely have seen in these letters an allusion to
the skeptical criterion.
Carneades formulated a three-step procedure for
determining the probability of an appearance. The first
step is to limit oneself to persuasive appearances, that
is, to those which appear to be in accord with the
objects from which they come, and from among these
appearances to select the ones that are not dim or
distant or in any way indistinct. The second step is
to inspect the persuasive appearance in the context
of the chain of apperances that accompany it. For
example, the appearances of a man brings with it ap-
pearances of his color, size, form, movement, speech,
clothing, and also of the air, light, day, sky, earth,
friends, and so forth. If none of these concomitant
appearances exerts a contrary pull by appearing false,
our confidence is increased. Sextus compares this
inspection to that of physicians who do not judge that
a man has a fever from one symptom alone but from
a concurrence (
syndrome) of symptoms, pulse, temper-
ature, color, and so forth. So the Academic looks for
a concurrence of appearances, none of which exerts
a contrary pull. When this condition is met, the initial
appearance may be said to be persuasive, with no pull
to the contrary. The third step is to examine closely
all of the concomitant appearances in order to assure
ourselves in each case that our vision is not dulled,
the distance is not too great or the object too small,
the duration of the appearance is not too short, etc.
When all these conditions are satisfied by all the
appearances, then the appearance with which we
began may be described as persuasive (pithane), having
no pull to the contrary (aperispastos), and examined
from all sides (periodeumene). The fullest account of
the Carneadean criterion is in Sextus (AM VII.166-84);
there is a shorter account in PH I.227-29. Cicero
alludes to the three stages but does not explain them
in Ac. II.33, 36; further, in II.105-10 he defends
Carneadean probability as an adequate guide in prac-
tical matters and in the arts. The later Pyrrhonists
rejected Carneadean probability as a departure from
true skepticism (cf. Photius, III, 119-20; PH I.229-30);
and indeed in this they had the support of Galen, who
took Carneadean probability to be equivalent to Stoic
apprehension (katalepsis) and to the formula, which
Galen himself preferred, that whatever appears clearly
to mind or senses is true (ed. Kühn, V, 778).
The charge that skepticism is self-contradictory ap-
pears most often in the following form: a person who
says that nothing can be known must admit that he
cannot know whether nothing can be known and
therefore must admit that perhaps something can be
known. Alternatively, if he claims to know that nothing
can be known he thereby admits that at least one thing
can be known and so contradicts his principle.
Metrodorus of Chios (quoted above, II) was no doubt
attempting to escape the second alternative when he
said, “We know nothing, not even whether we know
or do not know.” Similarly, according to Cicero (Ac.
I.45), Arcesilaus denied that anything could be known,
not even what Socrates left for himself (he knew that
he knew nothing; cf. Ac. II.74). Cicero also reports (Ac.
II.28) an exchange between Carneades and the Stoic
Antipater on this point. Antipater suggested that the
skeptic might make his position consistent by saying
that nothing can be comprehended except this one
thing, that nothing can be comprehended. Carneades,
however, insisted that there be no exceptions; the
person who states that nothing can be comprehended
must include this statement among the things that
cannot be comprehended. Lucretius probably echoes
the Carneadean view when he says, “If anyone thinks
that nothing is known, he also does not know whether
this can be known, since he confesses that he knows
nothing” (RN IV.469-70). The Academic Skeptics did
not escape the ambiguity of their presentation; they
were sometimes accused of affirming that nothing can
be comprehended (see above, III, 1). Sextus was more
cautious; he carefully avoided saying anything that
might seem to commit him to such an affirmation.
It was possible to state the charge of inconsistency
in terms of the ou mallon formula. Aristotle anticipated
the skeptics' dilemma when he said, in discussing
Heraclitus' supposed denial of the law of contradiction
(Metaphysics 1062b 2-9), that from Heraclitus' position
it would follow that just as when contradictory state-
ments are taken separately the affirmation is no more
true than the negation, so when the two together are
taken as a single affirmation, the entire affirmation will
be no more true than its negation. The answer of the
earlier skeptics to this criticism is not known; but
Sextus at least recognized its force. He saw that ou
mallon as a principle includes itself: it is no more true
than false and is therefore not a tenable position (PH
I.14). It was probably in response to this difficulty that
some skeptics compared ou mallon and other such
formulas to a purgative that eliminates itself along with
the arguments of the dogmatists (cf. DL IX.76; PE
XIV.18.21). Sextus offers another way out. The skepti-
cal ou mallon, he says, is not to be taken as an affirma-
tion or a negation but rather as a report of the skeptic's
inability to decide between conflicting statements. It
is a description of his state of mind and is as much
a question as a statement (PH I.15, 191-93, 200).
