The Eretrian school of Philosophy was originally the School of Elis

Elis

Elis, or Eleia is an ancient district that corresponds with the modern Elis peripheral unit...

where it had been founded by Phaedo of Elis

Phaedo of Elis

Phaedo of Elis was a Greek philosopher. A native of Elis, he was captured in war and sold into slavery. He subsequently came into contact with Socrates at Athens who warmly received him and had him freed. He was present at the death of Socrates, and Plato named one of his dialogues Phaedo...

; it was later transferred to Eretria

Eretria

Erétria was a polis in Ancient Greece, located on the western coast of the island of Euboea, south of Chalcis, facing the coast of Attica across the narrow Euboean Gulf. Eretria was an important Greek polis in the 6th/5th century BC. However, it lost its importance already in antiquity...

 by his pupil Menedemus

Menedemus

Menedemus of Eretria was a Greek philosopher and founder of the Eretrian school. He learned philosophy first in Athens, and then, with his friend Asclepiades, he subsequently studied under Stilpo and Phaedo of Elis. Nothing survives of his philosophical views apart from a few scattered remarks...

. It can be referred to as the Elis-Eretrian School, on the assumption that the views of the two schools were similar. It died out after the time of Menedemus (3rd century BC), and, consequently, very little is known about its tenets. Phaedo had been a pupil of Socrates

Socrates

Socrates was a classical Greek Athenian philosopher. Credited as one of the founders of Western philosophy, he is an enigmatic figure known chiefly through the accounts of later classical writers, especially the writings of his students Plato and Xenophon, and the plays of his contemporary ...

, and Plato

Plato

Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...

 named a dialogue, Phaedo

Phaedo

Plato's Phaedo is one of the great dialogues of his middle period, along with the Republic and the Symposium. The Phaedo, which depicts the death of Socrates, is also Plato's seventh and last dialogue to detail the philosopher's final days .In the dialogue, Socrates...

, in his honor, but it is not possible to infer his doctrines from the dialogue. Menedemus was a pupil of Stilpo

Stilpo

Stilpo was a Greek philosopher of the Megarian school. He was a contemporary of Theophrastus, Diodorus Cronus, and Crates of Thebes. None of his writings survive, he was interested in logic and dialectic, and he argued that the universal is fundamentally separated from the individual and concrete...

 at Megara

Megara

Megara is an ancient city in Attica, Greece. It lies in the northern section of the Isthmus of Corinth opposite the island of Salamis, which belonged to Megara in archaic times, before being taken by Athens. Megara was one of the four districts of Attica, embodied in the four mythic sons of King...

 before becoming a pupil of Phaedo; in later times, the views of his school were often linked with those of the Megarian school. Menedemus' friend and colleague in the Eretrian school was Asclepiades of Phlius

Asclepiades of Phlius

Asclepiades of Phlius was a Greek philosopher in the Eretrian school of philosophy. He was the friend of Menedemus of Eretria, and they both went to live in Megara and studied under Stilpo, before sailing to Elis to join Phaedo's school. His friendship with Menedemus was said to have been hardly...

.

Like the Megarians they seem to have believed in the individuality of "the Good," the denial of the plurality of virtue

Virtue

Virtue is moral excellence. A virtue is a positive trait or quality subjectively deemed to be morally excellent and thus is valued as a foundation of principle and good moral being....

, and of any real difference existing between the Good and the True. Cicero

Cicero

Marcus Tullius Cicero , was a Roman philosopher, statesman, lawyer, political theorist, and Roman constitutionalist. He came from a wealthy municipal family of the equestrian order, and is widely considered one of Rome's greatest orators and prose stylists.He introduced the Romans to the chief...

 tells us that they placed all good in the mind

Mind

The concept of mind is understood in many different ways by many different traditions, ranging from panpsychism and animism to traditional and organized religious views, as well as secular and materialist philosophies. Most agree that minds are constituted by conscious experience and intelligent...

, and in that acuteness of mind by which the truth

Truth

Truth has a variety of meanings, such as the state of being in accord with fact or reality. It can also mean having fidelity to an original or to a standard or ideal. In a common usage, it also means constancy or sincerity in action or character...

 is discerned. They denied that truth could be inferred by negative categorical proposition

Proposition

In logic and philosophy, the term proposition refers to either the "content" or "meaning" of a meaningful declarative sentence or the pattern of symbols, marks, or sounds that make up a meaningful declarative sentence...

s, and would only allow positive ones, and of these only simple ones.