Mnesarchus or Mnesarch of Athens, was a Stoic

STOIC

STOIC was a variant of Forth.It started out at the MIT and Harvard Biomedical Engineering Centre in Boston, and was written in the mid 1970s by Jonathan Sachs...

 philosopher, lived c. 160-c. 85 BC.

He was a pupil of Diogenes of Babylon and Antipater of Tarsus

Antipater of Tarsus

Antipater of Tarsus was a Stoic philosopher. He was the pupil and successor of Diogenes of Babylon as leader of the Stoic school, and was the teacher of Panaetius...

. 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...

 says that he was one of the leaders of the Stoic school at Athens

Athens

Athens , is the capital and largest city of Greece. Athens dominates the Attica region and is one of the world's oldest cities, as its recorded history spans around 3,400 years. Classical Athens was a powerful city-state...

 together with Dardanus

Dardanus of Athens

Dardanus , of Athens, was a Stoic philosopher, lived c. 160-c. 85 BC.He was a pupil of Diogenes of Babylon and Antipater of Tarsus. Cicero mentions him as being one of the leaders of the Stoic school at Athens together with Mnesarchus at a time when Antiochus of Ascalon was turning away from...

 at a time when Antiochus of Ascalon

Antiochus of Ascalon

Antiochus , of Ascalon, , was an Academic philosopher. He was a pupil of Philo of Larissa at the Academy, but he diverged from the Academic skepticism of Philo and his predecessors...

 was turning away from scepticism

Philosophical skepticism

Philosophical skepticism is both a philosophical school of thought and a method that crosses disciplines and cultures. Many skeptics critically examine the meaning systems of their times, and this examination often results in a position of ambiguity or doubt...

 (c. 95 BC). He was the teacher of Antiochus for a time, and he may also have taught Philo of Larissa

Philo of Larissa

Philo of Larissa, was a Greek philosopher. He was a pupil of Clitomachus, whom he succeeded as head of the Academy. During the Mithradatic wars which would see the destruction of the Academy, he travelled to Rome where Cicero heard him lecture. None of his writings survive...

. After the death of Panaetius

Panaetius

Panaetius of Rhodes was a Stoic philosopher. He was a pupil of Diogenes of Babylon and Antipater of Tarsus in Athens, before moving to Rome where he did much to introduce Stoic doctrines to the city. After the death of Scipio in 129, he returned to the Stoic school in Athens, and was its last...

(109 BC), the Stoic school at Athens seems to have fragmented, and Mnesarchus was probably one of several leading Stoics teaching in this era. He was probably dead by the time Cicero was learning philosophy in Athens in 79 BC.

Cicero mentions him several times and seems to have been familiar with some of his writings:

Mnesarchus himself, said, that those whom we call orators were nothing but a set of mechanics with glib and well-practised tongues, but that no one could be an orator but a man of true wisdom; and that eloquence itself, as it consisted in the art of speaking well, was a kind of virtue, and that he who possessed one virtue possessed all, and that virtues were in themselves equal and alike; and thus he who was eloquent possessed all virtues, and was a man of true wisdom.