Pompey had been elected sole consul in…

51 BCE

Pompey had been elected sole consul in 52 BCE and given a five-year provincial command in Spain; Caesar in the same year had been allowed by a law sponsored by all ten tribunes to stand for the consulship in absentia.

If he is to stand in 49 BCE for the consulship for 48 BCE, he will be out of office, and therefore in danger, during the last ten months of 49 BCE.

As a safeguard for Caesar against this, there seems to be an understanding—possibly a private one made at Luca in 56 BCE between him and Pompey—that the question of a successor to Caesar in his commands shall not be raised in the Senate before March 1, 50 BCE.

This maneuver should ensure that Caesar will retain his commands until the end of 49 BCE; however, the question of replacing Caesar is actually raised in the Senate a number of times from 51 BCE onward.

Greek philosopher Posidonius, a member of the Stoic school who taught at Rhodes and in Rome and had been heard by the young Cicero, is an eclectic thinker who writes extensively on natural science and in defense of divination.

Combining Stoic doctrines with ideas drawn from Plato and Aristotle, Posidonius has modified the Stoic view of the human soul by accepting a Platonic-Aristotelian division within it into "rational" and "irrational."

Posidonius is celebrated as a polymath throughout the Graeco-Roman world because he comes near to mastering all the knowledge of his time, similar to Aristotle and Eratosthenes.

He attempts to create a unified system for understanding the human intellect and the universe that will provide an explanation of and a guide for human behavior.

The major source of materials on the Celts of Gaul, Posidonius is profusely quoted by Timagenes, Julius Caesar, the Sicilian Greek Diodorus Siculus, and the Greek geographer Strabo. (The writings of Posidonius, who reportedly wrote a "completion" of Plato's “Timaeus,” survive only in fragments.)

In his own era, his writings on almost all the principal divisions of philosophy have made Posidonius a renowned international figure throughout the Graeco-Roman world.

He is widely cited by his contemporary and near-contemporary writers, including Cicero, Livy, Plutarch, Strabo (who calls Posidonius "the most learned of all philosophers of my time"), Cleomedes, Seneca the Younger, Diodorus Siculus (who uses Posidonius as a source for his Bibliotheca historia ["Historical Library"]), and others.

Posidonius is acclaimed during his life for his literary ability and as a stylist, although his ornate and rhetorical style of writing will pass out of fashion soon after his death in 51.

From 54 to 51 BCE, Cicero has written the six books of De re publica (”On the Commonwealth”), in which he advances the first full-blown theory of natural law:” “True law is right reason in accord with nature; it is of universal application, unchanging and everlasting...."

The work is written in the format of a Socratic dialogue in which Scipio Africanus Minor (who had died a few decades before Cicero was born, several centuries after Socrates' death) takes the role of a wise old man — an obligatory part for the genre.

Cicero's treatise is politically controversial: by choosing the format of a philosophical dialogue he avoids naming his political adversaries directly.

Cicero employs various speakers to raise differing opinions in an attempt to make it more difficult for these adversaries to take him to task on what he has written.