Sources. Pyrrho, the chief Sceptic of this period, left no
writings. Of the writings of his earlier followers very few fragments
have come down to us. We are obliged, therefore, to rely on
secondary sources, such as Diogenes Laertius, Aristocles
(quoted by Eusebius), and the Later Sceptics. 
The Stoics and Epicureans laid down certain theoretical principles from
which they deduced canons of conduct, always keeping in view the
practical aim of philosophy, to make men happy. The Sceptics agreed
with the Stoics and Epicureans in referring philosophy primarily to
conduct and the pursuit of happiness, but, instead of laying down
theoretical principles as the Stoics and Epicureans had done, they
taught that the first step to happiness is to forego all theoretical
inquiry and to disclaim all certainty of knowledge.
The principal Sceptics are: (1) Pyrrho, (2) the Platonists of
the Middle Academy, (3) Later Sceptics, including
Life. Pyrrho of Elis was a contemporary of Aristotle. Very
little is known about his life. It is probable that he died about the
year 270 B.C. Among his disciples Timon of Phlius, surnamed the
sillographer, is best known. Timon composed satirical poems
(silloi) in which he attacked the dogmatists, following in this
the example of his teacher, who declared that Democritus alone deserved
the name of philosopher, and that all the rest, Plato and Aristotle
included, were mere Sophists.
In accounting for Pyrrho's Scepticism it is safe to add to the
influence which Democritus may have exercised on his mind
the influence of the Megarian spirit of criticism which must have
prevailed in Pyrrho's native city.
All we know about the teaching of Pyrrho may be reduced to the
following propositions: (1) In themselves, real things are neither
beautiful nor ugly, neither large nor small. We have as little right to
say that they are the one as we have to say that they are the other.
Hence the famous ouden mallon.  (2) Real things are,
therefore, inaccessible to human knowledge, and he is wise who,
recognizing the futility of inquiry, abstains from judging. This
attitude of mind was called epochê aphasia.  (3) From
this withholding of judgment arises the state of
imperturbability (ataraxia) in which human happiness
 Cf. Diog. Laer., IX, 61.
 Op. cit., IX, 103.
 Aristocles, quoted by Eusebius, Praeparatio Evangelica, XIV,
18, apud Migne, Patr. Graeca, Vol. XXI, coll. 1216 ff.
In this account of Pyrrhonism no attempt has been made to separate the
doctrines of Pyrrho from those of Timon. Pyrrho taught orally, and the
fact of his having left no writings accounts for the freedom with
which writers attribute to him the principles and tenets of his
THE MIDDLE ACADEMY
Arcesilaus and Carneades, departing from the tradition of
the Platonic school, of which they were the official representatives,
lent their aid to the Sceptical movement by seeking to establish on
rational and empirical grounds the thesis that it is impossible to
arrive at certitude.  The Scepticism of the Middle Academy very quickly
gave way before Eclecticism.
 Cf. p. 123.
THE LATER SCEPTICS
Under this title are included AEnesidemus and others who were
for the most part physicians, and who from sensualistic premises
deduced a system of Scepticism which was more radical than the
idealistic Scepticism or the probabilism of the Academy.
AEnesidemus of Cnossus in Crete taught at Alexandria about the
beginning of the Christian era. According to Ritter and Preller,  he
flourished between the years 80 and 50 B.C. Diogenes  alludes to a
work of AEnesidemus in which by means of ten tropes
(tropoi) he strove to show that contradictory predicates may be
affirmed of one and the same subject, and that, consequently, certain
knowledge is impossible. These tropes are a fairly complete enumeration
of the arguments of the Sceptics and furnished, directly or indirectly,
material to more than one advocate of the relativity of knowledge in
 Op. cit., p. 570.
 IX, 106.
According to Sextus Empiricus,  AEnesidemus subjected the notion of
cause to special analysis, and pronounced it to be
self-contradictory. A cause, he argued, either precedes the effect, or
is synchronous with it, or is subsequent to it. Now, it cannot precede
the effect; if it did, it would be a cause before it was a cause. It
cannot be synchronous with the effect, for in that case cause and
effect would be interchangeable; there would be no reason why one
rather than the other should be called the product. Finally, the
hypothesis that the cause is subsequent to the effect is manifestly
absurd. In this way did AEnesidemus conclude, sophistically, that
the notion of cause is utterly devoid of meaning.
 Mathem., IX, 220.
AEnesidemus, however, did not regard Scepticism as a system, but only
as an introduction (agôgê) to a system of philosophy.
Agrippa, who lived about a century after AEnesidemus, reduced
the tropes to five, and argued that knowledge is impossible because,
the major premise of the syllogism being itself a conclusion,
syllogistic reasoning is a regressus in infinitum.
Sextus Empiricus, who is the most important of the later
Sceptics, lived at Alexandria about the year A.D. 300. In his work
Against the Mathematicians, and in his treatise known as
Pyrrhonic Hypotyposes, he subjects to critical examination the
dogmatism not only of the great constructive systems of theoretical and
practical philosophy but also of arithmetic and geometry. He maintains
that no science is certain, or rather that the true Sceptic should
refrain from any absolute judgment whatever.
Historical Position. The history of Greek Scepticism exhibits an
interesting phase of the practical idea which dominated the philosophy
of Greece during the third period. Like the Stoics and Epicureans, the
Sceptics were animated with the desire to find in philosophy a refuge
from the disheartening conditions of the times in which they lived;
but, unlike their dogmatizing contemporaries, they believed that the
first step towards securing happiness is the abdication of all claim to
the attainment of scientific knowledge.