## 1. Historical and biographical information



The name 'Dialectical School' is used for a group of
philosophers active from the later 4th to the mid 3rd centuries BC who
are referred to as members of the Dialectic sect (*hairesis*)
or as dialecticians (*dialektikoi*) in some later ancient
sources (Diogenes Laertius [DL] 1.19). Together with the Megarics,
Cyrenaics and Cynics, the Dialecticians count among the minor Socratic
schools. Their main philosophical interest was in dialectical skill
and accomplishment, including the development and resolution of
logical paradoxes. They also made several important positive
contributions to the development of propositional logic.



The Dialecticians were traditionally counted among the philosophers of
the Megaric School, founded by Euclides of Megara, author of Socratic
dialogues (Grote 1885, 1:140; M. Kneale 1937; Mates 1953; Prior 1955;
W. C. Kneale and Kneale 1962, 117). In antiquity, the best-known
figure from the Megaric School was Stilpo, who, like Euclides, was a
native of Megara. For reasons that will become clear, scholars now
typically use 'Mergaric' as the adjective describing a
philosophical grouping or position, while reserving
'Megarian' as an adjective describing an origin in city of
Megara (the same distinction is marked in Ancient Greek). More recent
scholarship has placed Diodorus and Philo in a Dialectical School,
separate from the Megaric School (Sedley 1977, 75 followed by Bobzien
2011; Algra 1999, 47; Ebert 1991; Ebert 2008). In fact, disagreement
over the existence of a Dialectical Sect went back to
antiquity. Diogenes Laertius holds that the Dialecticians are a
separate 'ethical' sect, founded by Clinomachus, but tells
us that an earlier historian, Hippobotus, does not think the
Dialectical is a separate sect (DL 1.19).



But the modern scholarly reason for positing the Dialectical School as
separate from the Megaric School has four basic elements.


1. We should distinguish a 'lineage' (*diadoche*)
from a 'sect' (*hairesis*), which are the two main
ways ancient historiographers grouped philosophers. The first is the
genealogy of a philosopher in terms of teacher-student relationships.
The second is a 'school' in the sense of set of
philosophers with a shared core of doctrines, and some institutional
connection, for example a series of scholarchs. Everyone agrees that
Diodorus and Philo are in the lineage of Euclides of Megara.
2. There was a Megaric Sect, which included at least Euclides and
Stilpo of Megara.
3. There was a Dialectical Sect, identified by 4th and 3rd century
contemporaries, which was not just a phase of or part of the Megaric
sect. It included Diodorus and Philo.
4. The Dialectical Sect was one of the ten ethical sects identified
by Diogenes Laertius (DL 1.19).



(3) is the important claim for establishing that there was a separate
Dialectical School. Sedley defends (3) with the following argument:
Stilpo won over three students 'from the Dialecticians'
(DL 2.114). Since Stilpo was a member of the Megaric School this must
mean that the 'Dialecticians' were a separate, and rival,
group from Stilpo's Megaric sect (Sedley 1977, 75-76).



Some try to reject Sedley's conclusion by admitting that the
Dialecticians were a group that was identified in antiquity as
separate from the Megaric sect, but the Dialectical group was not,
strictly, a sect in the technical sense used by ancient
historiographers. The is because the Dialectical group lacked the
required institutional framework, such as a succession of scholarchs
or core set of doctrines (DL 1.20; Doring 1989, 309; cf. Allen
2018, 44-46). But, of course, the Megarics also lacked such a
structure. On (4), the evidence that the Dialectical group is
identical to the Dialecticians mentioned at (DL 1.19), or even that
there was such a sect, is weak. Diogenes places the Dialectical sect
in a set of ethical sects, but no evidence attributes to any putative
member of the sect any ethical views (unless one holds that fatalism
is an ethical view). We can safely call Diodorus and Philo
Dialecticians in the sense of belonging to a distinctive philosophical
group, rival to Stilpo's circle, but sharing a philosophical
genealogy with it. Whether this group was the Dialectical Sect, or a
sect at all, in the sense used by ancient historiographers, is less
certain because we do not know whether the members of the Dialectical
School were connected by an institution comparable to other ancient
philosophical schools, or whether their union under one name in later
reports was based more loosely on their common philosophical
interest in dialectic.




Those later reports give Clinomachus of Thurii, a pupil of Eubulides
of Miletus, as founder of the school, but may have been given this
title only in hindsight (DL 1.19 and 2.112, Sedley 1977 n.16).
Euphantus of Olyntus, another pupil of Eubulides, probably born before
349 BC, may have been the earliest member of the school. The name
'Dialectical School' is reported to have been introduced
by its member Dionysius of Chalcedon, active around 320 BC because of
the practice of putting arguments in question and answer form (DL
2.106; Castagnoli 2010, 157).



The most important philosopher of the sect is Dionysius'
contemporary, Diodorus Cronus, who taught in Athens and Alexandria
around 315-284 BC. He left no writings but is the most
influential member of the Dialectical School. Diodorus' most
famous pupil is Zeno of Citium, founder Stoicism. The dialectician
Aristides belongs to the same generation as Diodorus Cronus. Alexinus
(c. 339-265) may have belonged to the sect. The second important
philosopher of the Dialectical School is the logician Philo (sometimes
referred to as Philo of Megara, although we do not know his city of
origin); he studied with Diodorus. He wrote a dialogue
*Menexenos* and possibly a work *On Signs* and a work
*On Schemata*. All of these are lost. Diodorus Cronus'
five daughters Menexene, Argeia, Theognis, Artemisia and Pantacleia
are all said to have been logicians, and thus may have belonged to the
school. Finally, the dialectician Panthoides flourished
c.280-275 BC, and the dialecticians Aristoteles and Artemidorus
can be dated around 250 BC.



Original philosophical contributions are testified only for Diodorus
Cronus and Philo, in the areas of logic, language and theory of motion
(for more on Diodorus' contributions see entries
 Ancient Atomism
 and
 Diodorus Cronus);
 their views on logic were influential on Stoic logic, which in turn
anticipated many of the developments in 20th century logic.
Philosophers of the Dialectic sect had an impact also on Epicurean,
Peripatetic, and Sceptic philosophy, and seem to have interacted in
discussion with members of most Hellenistic philosophical schools.
Diodorus Cronus' modal theory and his Master Argument served as
a major philosophical inspiration for
 Arthur Prior.