What it was
The Senate was a standing council of former magistrates, some three hundred strong in the middle Republic and roughly doubled by Sulla. Membership was for life, subject to the censors' revision.
It was formally an advisory body. Its resolutions were senatus consulta — advice to a magistrate — and did not have the force of law. That formal weakness is the most important thing to understand about it, because in practice it governed.
How it worked
It was convened by a magistrate with the right to do so, who set the business. Members were asked their opinion in order of rank, which meant senior ex-consuls spoke first and shaped the debate before junior members were reached.
Its practical authority came from three things: its members held all the magistracies in turn, so ignoring the Senate meant ignoring one's own future colleagues; it controlled the treasury and the allocation of provinces; and it directed foreign policy and received embassies.
Powers and limits
It could not legislate, could not command an army and could not try most cases. It could allocate money, assign commands, extend imperium, and declare a state of emergency through the senatus consultum ultimum.
Its limit was the tribunes' veto and the sovereignty of the assemblies, which could and did legislate against senatorial advice — the mechanism the Gracchi and their successors used.
How it changed
Sulla enlarged it and made the quaestorship the automatic route in. Caesar enlarged it further and admitted provincials, which caused offence recorded in surviving jokes and graffiti.
Under the Principate it gained judicial functions and lost political initiative. Tacitus's account of senatorial business under Tiberius is a study of a body performing deliberation in the presence of someone who has already decided.
What the evidence supports
Senatus consulta were formally advice.
Attested in the constitutional sources and in the formulae of the decrees themselves. Their binding force was practical rather than legal.
The Senate's authority rested on controlling finance and provincial assignments.
Polybius identifies precisely this in analysing where power actually lay, and he was writing in Rome while the system was still working — a contemporary observer rather than a later reconstruction.
How far the Senate was ever genuinely deliberative is argued.
Speaking order by rank, the weight of a few consular families and the density of family alliance all suggest outcomes were often settled before debate. How often is not recoverable.
Terms
- senatus consultum
- A resolution of the Senate: formally advice to a magistrate.
- senatus consultum ultimum
- The emergency decree instructing magistrates to see that the state took no harm.
- princeps senatus
- The senior member, asked his view first — the title behind princeps and so behind the Principate.
Primary sources
Polybius, Histories 6.13
Where power actually lay: the Senate's control of the treasury, of provinces and of foreign embassies.
Tacitus, Annals 1.7-15, 3.65
The Senate under Tiberius, described by a senator with contempt for what it had become.
Cicero, Letters to Atticus
Senatorial business as reported privately by a participant.
Covered elsewhere
- Military command and the officer corps is treated in the warfare encyclopedia: Command structure. Who commanded on campaign, on what authority, and what happened when a constitution put two men in charge of one army — covered there, including the alternating consular command at Cannae.
How to read the evidence labels
- Evidence level: Documented
- Supported by a named primary text or by excavated material evidence.
- Evidence level: Probable
- Supported by strong inference that most specialists accept.
- Evidence level: Disputed
- Substantial specialist disagreement exists; competing readings are stated.
- Evidence level: Literary
- Belongs to poetic or mythological construction rather than to history.
- Evidence level: Mythological
- Belongs to shared religious or mythic tradition rather than to any single text.
- Evidence level: Unknown
- The available evidence is insufficient to decide.
These labels describe the status of the evidence, not our confidence in a conclusion. A claim marked Literary is not a claim we doubt; it is a claim about what kind of thing a poem is.