[4] The elder Cato was famed for his austerity and traditional Roman values,[5] which was affected for political reasons[6] and meant to embellish his reputation as "the foremost representative of the mos maiorum".

[8] After Drusus' death and the resulting start of the Social war in 91 BC, Cato and his sister probably came into the household of his mother's older brother, Mamercus Aemilius Lepidus Livianus.

[10] Cato was especially close to his half-brother, Gnaeus Servilius Caepio, and his elder half-sister, Servilia, who would later marry Marcus Junius Brutus (the father of the tyrannicide) and become the mistress of Julius Caesar.

He made a deliberate decision to break with the norms of his peers... faced [with] daunting challenges in his intended political career[,] he leveraged his strongest asset – his great-grandfather's reputation as a champion of tradition – to enhance his own status.

[28] In 72 BC, Cato volunteered to fight in the war against Spartacus, presumably to support his half-brother Caepio, who was serving as a military tribune in the consular army of Lucius Gellius.

[30] After winning election, he was dispatched to Macedonia under propraetor Marcus Rubrius, where he earned the respect of the soldiers by sharing their burdens and treating them justly.

Cato was overwhelmed by grief and, ignoring Stoic principles of apatheia (living without passions), he spared no expense to organise lavish funeral ceremonies.

[37] Around this time, Lucullus – one of the wealthiest men in Rome and long-time commander of troops against Mithridates VI Eupator in the Third Mithridatic War – approached him about marrying Cato's younger half-sister Servilia.

[43] In doing so, he cooperated with Julius Caesar, who had then just completed a term as curule aedile and was acting as a prosecutor in court, in challenging the legal immunity and payments given to men who had received bounties for killings during the Sullan proscriptions.

[40] On his last day in the aerarium, Plutarch reports that he discovered that his old friend and colleague in the urban quaestorship, Marcus Claudius Marcellus, was entering fraudulent records; Cato apparently stormed back to erase them before the end of his term.

[46] After his election but before his term started in December, he opposed granting additional honours to Pompey, engaged in an unsuccessful prosecution of Lucius Licinius Murena, and took part in a famous debate on the Catilinarian conspiracy.

Upon discovery of an associated plot against the lives of the consuls and other magistrates in Rome, Cicero arrested the conspirators within the city and proposed executing them without trial, a violation of citizen rights to appeal.

[51] While Caesar's speech – due to the fact he was praetor-elect and would soon assume a presidency of one of the permanent courts – seemed to imply he would as a judge support a prosecution for murder, Cato's counter-arguments convinced the senators to act aggressively and decisively by playing on their fears.

Cato's push against bribery was opposed by some of his normal allies, such as Cicero, who believed that it undermined senatorial government in alienating the equestrians, and was eventually dropped.

[81] For Fred Drogula, Cato's posturing as "the voice of the ancestors enabled him to push or shame others into agreeing with his opinions", which also helped to make up for his meagre financial resources in an expensive political environment where large bribes paid to voters was a normal part of campaigning.

[91] In response, Cato again championed legislation banning bribery (proposed by a tribune named Marcus Aufidius Lurco), which was defeated, in part because the voters liked receiving payments for their votes.

[127] Modern historians also see another reason: there was little productive to do in Rome when triumviral allies controlled all the major magistracies; leaving for Cyprus would allow Cato to buttress his reputation as an honest governor while waiting for the political winds to shift.

[142] At the debate that year about the lex Trebonia to grant Crassus the province of Syria so he could fight a war of choice against the Parthian Empire, Cato again repeated his tactic of filibustering until his opponents had him arrested so he could claim to be poorly treated.

[149] One case was that against Aulus Gabinius, who was convicted for receiving a ten thousand talent bribe from Ptolemy XII Auletes to invade Egypt and place him back on the throne.

The ancient sources believe that the delays were artificially created to justify the creation of Pompey as dictator, calls which Cato and senators such as Marcus Junius Brutus,[156] strongly opposed.

[157] After Cato praised Pompey on his civic-mindedness in publicly refusing a possible dictatorship, the political situation stabilised and two conservative consuls, Gnaeus Domitius Calvinus and Marcus Valerius Messalla Rufus, were elected in July 53 BC.

[167] Some modern historians, such as John T Ramsey, however, conceive of the choice in political terms: the obstructive tribunes wanted to prosecute Milo for Clodius' murder, which could not happen if he were elected to the consulship and gained legal immunity.

[179] Attempts to recall Caesar from Gaul started in earnest in 51 BC under consul Marcus Claudius Marcellus (Cato's former quaestorian colleague).

[188] By the weeks before the start of the war in early January 49 BC, Cato, Pompey, and their allies had hardened their political position to the point where they were unwilling to offer any concessions at all.

[193] When Caesar offered peace terms on 23 January that he would be willing to lay down his command and stand for a consulship in person in return for amnesty and Pompey's departure to Spain, Cicero relates that Cato strongly supported the plan and forced himself into the war council at which the proposal was discussed.

[204] Left behind in command at Dyrrhachium, also possibly for political reasons to remove critics (including Cicero) from decision-making following a prospective Pompeian victory, Cato received news of the defeat from Titus Labienus.

His thrust, however, was somewhat feeble... [and] he did not at once dispatch himself... His servants heard the noise and cried out, and his son at once ran in, together with his friends... [A] physician went to him and tried to replace his bowels, which remained uninjured, and to sew up the wound.

[221][105] His policies with regard to stopping powerful politicians such as Pompey, Caesar, and Crassus alienated – through its very success – them from the rest of the senatorial class, leading to the formation of their alliance in 59 BC.

[222] Many scholars believe that Cato's political strategy before 49 BC contributed significantly in starting the civil war that was the proximate cause of the collapse of the Roman republic, even if he did not intend for conflict.

[235][236] Some scholars point to how Cato acted in ways profoundly inconsistent with Stoic tenets: his anger at the breaking of his betrothal to Aemilia Lepida, breakdown over the death of his half-brother Caepio, his visible despair at the sight of casualties from the civil wars, etc.