Society
The Legion proper is first and foremost a slave army, the sole owner of which is Caesar. As Caesar conquers the peoples of the wasteland, he strips them of their tribal identities and merges them into his forces. There is no other tribe than the Legion itself. The non-tribal people who live in Legion-controlled territory are not considered legionaries. They are subjects of the Legion, living in the cities and towns under its control, and are generally left free to do whatever they wish, as long as they do not interfere with Legion operations or endanger its position.
The brutality of the Legion is a major problem for many, but it also brings benefits. Arizona was once a lawless wasteland, thick with raiders and other threats to the point where crossing two miles without a clash with raiders was considered rare. The Legion brought peace and stability to the entire state by exterminating and enslaving the raider tribes. However, despite this brutal subjugation and the relative peace it brought, the Legion does little to actually govern its territory in the traditional sense, possessing almost no civil institutions or permanent infrastructure, instead relying on tribute extracted from those living in their territory to continue expanding.
The focus of the Legion's ideology is survival and long term stability at all costs. Caesar disregards democracies as ineffective, fostering corruption, and disintegration. In Caesar's view, Ancient Rome was a militarized autocracy that effectively assimilated the cultures it conquered, which he saw as the perfect template for a society that would survive and thrive in the face of the challenges of the post-nuclear world. By dedicating its members to a higher ideal, he seeks to prevent humanity from fracturing and destroying itself again. He believes that the only way to achieve this is through enforcing a nationalist, imperialist, totalitarian, homogeneous culture that obliterates the identity of every group it conquers. The individual has no value beyond his utility to the state, whether as an instrument of war or production.
A natural consequence of this is the emphasis placed on personal sacrifice. Victory cannot be achieved without sacrificing blood and life. To this end, the Legion shuns robots, as they firmly believe that mankind requires warriors and their sacrifice, rather than gadgets that allow for bloodless victories. The Legion also forbids painkillers and other chems (including medically beneficial chems like stimpaks) as detrimental to the human condition and Caesar's long-term plans to reshape humanity. Ignorance of medical science among the legionaries also ensures that only the hardiest will survive and go on to become deadly veterans.
Politically, this philosophy is expressed in a general disdain for democracy as a weak and ineffective system that fosters disunity, greed, and self-interest at the expense of the collective and the greater good. Caesar cites the NCR as an example, focusing on government corruption by wealthy brahmin barons and landowners, greed permeating every level of society, all leading to the abandonment of the collective and the greater good. The Legion is intended to be the Republic's opposite, shunning democracy in favor of a strong, centralized rule that would prevent fragmentation and internal weakness. The conquest of NCR will establish a new order, akin to the Roman Empire, complete with the transformation of the Legion from a marauding army into a domestic military force.
This opposition is based on a loose interpretation of Hegelian dialectics, where the thesis (NCR) and the antithesis (Caesar's Legion) will inevitably form a synthesis at the resolution of the conflict, eliminating flaws and leaving a new quality, with common elements and ideas. He likens the situation between the NCR and the Legion to the transformation of the ancient Roman Republic into the Roman Empire.
Social Structure
The Legion employs a very strict hierarchy and clear division of roles between the sexes. Legionaries are the main fighting force of the Legion, composed of able-bodied men enslaved by the Legion or born into it. They have only one purpose: to fight for Caesar until they fall in battle. This principle is imprinted into each legionary during his reconditioning or upbringing (for those born into slavery), creating fanatically loyal soldiers. Unlike the Roman Empire, experience and veteran status have no bearing on a legionary's position. While they receive better equipment as they advance, this is solely for the purpose of accomplishing more dangerous and complex tasks, with much smaller tolerance for failure. They have no personal freedoms or rights. Their only real choice is where and when they die for Caesar, to whom they are disposable tools, discarded the moment they stop fulfilling their purpose.
Women are expressly forbidden from fighting, being considered breeding stock as well as being treated as money to be rewarded among Legionaries. They are caretakers, healers, midwives, and breeders, fulfilling roles essential to maintaining the Legion's continuous campaign of expansion. Of particular note are the priestesses, who raise children taken from their parents and raise them in keeping with Caesar's doctrine.
Many members of the Legion express condescending or misogynistic opinions of women and their non-combat roles. The Legion justifies the sexist segregation of genders in their society with the principle of minimax, Caesar strictly divides the duties between the sexes in order to fully utilize their potential and optimize the Legion's might. By forbidding women from engaging in combat, he increases the likelihood of their bearing of children, especially necessary due to the high infant mortality resulting from the low level of medical care. Population growth is required for expansion, providing a greater number of warriors to use in military campaigns. Caesar himself is not particularly prejudiced against any sex, or rather, treats them both instrumentally, like pawns on a chessboard.
In order to maximize breeding and eliminate factors that might lower it, Caesar has decreed homosexuality a capital offense and mandated child quotas from all legionaries.
Despite this, it is believed that by many in the NCR and even in the Brotherhood of Steel that - similarly to the actual Roman empire - homosexuality is present within the military but on either a "don't ask, don't tell" basis to openly gay relationships. Veronica, when asked about the Legion, states that they "Mount their soldiers as much as they mount their women." Cass also states to a male Courier with the Confirmed Bachelor perk when asked about caravan life that she "doesn't like soft living or soft men" to which the Courier may reveal his lack of sexual or romantic interest in women leading Cass to state that he has a "Legion outlook on things". Major Knight also confides to a male homosexual Courier that the Legion is "a little more forgiving about... friendships."
It is unclear how the Legion views cannibalism, but it does not dissuade Caesar from working with members of the White Glove Society to further his goals. It is also believed by some NCR citizens that those in the Legion practice cannibalism.
The Legion evidently tolerates submissive mutants, or at least ghouls. Due to their limited numbers, Caesar does not consider super mutants and ghouls as a relevant issue.