Final answer:
Cicero compares the authority of the Roman Senate to the power of the magistrates.
Step-by-step explanation:
In the Roman Senate, Cicero compares the authority of the Senate to the power of the magistrates. Although the Senate's decrees were technically advice, the magistrates generally followed them. The Senate's authority expanded over time as the power of the legislative assemblies declined, and it eventually took a greater role in civil law-making. Cicero used this comparison to highlight the significance and influence of the Senate in Roman governance.