This volume is the first part of the palingenesis of the senatus consulta of republican and imperial Rome. It represents the result of a collaborative research effort that brings ancient sources back to the centre of scientific debate in all their complexity, starting with the way they were created and how they have been handed down through history. It presents the reconstruction and commentary on the decrees of the Roman Senate issued between 509 BC and 367 BC, a significant period marked by the pivotal struggle for equality between the patrician and the plebeian orders. Even in this early phase of Roman legal experience, it is already possible to glimpse the original core of the working mechanisms of the res publica, especially in terms of the dialectic between the Senate and the magistrates, which would also bind the political and institutional development of the subsequent phases.