The sum of his power derived first of all from various powers of office delegated to him by the Senate and people, secondly from his immense private fortune, and thirdly from numerous patron-client relationships he established with individuals and groups throughout the Empire. All of them taken together formed the basis of his auctoritas, which he himself emphasized as the foundation of his political actions.
The Anglo-Irish Writer Jonathan Swift (1667–1745), in his Discourse on the Contests and Dissentions in Athens and Rome, criticized Augustus for installing tyranny over Rome, and likened what he believed Great Britain's virtuous constitutional monarchy to Rome's moral Republic of the 2nd century BC. In his criticism of Augustus, the admiral and Historian Thomas Gordon (1658–1741) compared Augustus to the puritanical tyrant Oliver Cromwell (1599–1658). Thomas Gordon and the French political Philosopher Montesquieu (1689–1755) both remarked that Augustus was a coward in battle. In his Memoirs of the Court of Augustus, the Scottish scholar Thomas Blackwell (1701–1757) deemed Augustus a Machiavellian ruler, "a bloodthirsty vindicative usurper", "wicked and worthless", "a mean spirit", and a "tyrant".
One of the most enduring institutions of Augustus was the establishment of the Praetorian Guard in 27 BC, originally a personal bodyguard unit on the battlefield that evolved into an imperial guard as well as an important political force in Rome. They had the power to intimidate the Senate, install new emperors, and depose ones they disliked; the last Emperor they served was Maxentius, as it was Constantine I who disbanded them in the early 4th century and destroyed their barracks, the Castra Praetoria.
The month of August (Latin: Augustus) is named after Augustus; until his time it was called Sextilis (named so because it had been the sixth month of the original Roman calendar and the Latin word for six is sex). Commonly repeated lore has it that August has 31 days because Augustus wanted his month to match the length of Julius Caesar's July, but this is an invention of the 13th century scholar Johannes de Sacrobosco. Sextilis in fact had 31 days before it was renamed, and it was not chosen for its length (see Julian calendar). According to a senatus consultum quoted by Macrobius, Sextilis was renamed to honor Augustus because several of the most significant events in his rise to power, culminating in the fall of Alexandria, fell in that month.
Tacitus was of the belief that Nerva (r. 96–98) successfully "mingled two formerly alien ideas, principate and liberty". The 3rd-century Historian Cassius Dio acknowledged Augustus as a benign, moderate ruler, yet like most other historians after the death of Augustus, Dio viewed Augustus as an autocrat. The poet Marcus Annaeus Lucanus (AD 39–65) was of the opinion that Caesar's victory over Pompey and the fall of Cato the Younger (95 BC–46 BC) marked the end of traditional liberty in Rome; Historian Chester G. Starr, Jr. writes of his avoidance of criticizing Augustus, "perhaps Augustus was too sacred a figure to accuse directly."
Also, Historian R. Shaw-Smith points to letters of Augustus to Tiberius which display affection towards Tiberius and high regard for his military merits. Shotter states that Tiberius focused his anger and criticism on Gaius Asinius Gallus (for marrying Vipsania after Augustus forced Tiberius to divorce her), as well as toward the two young Caesars, Gaius and Lucius—instead of Augustus, the real Architect of his divorce and imperial demotion.