Senecio's origins are unknown. He has been identified as the subject of an inscription where the name of the subject is lost, which provides us his cursus honorum. The earliest office recorded on this inscription was quattuorviri viarum curandarum, one of the four boards that comprised the vigintiviri; membership in one of these was a required first step toward a gaining entry into the Roman Senate. His next recorded office was as quaestor of the public province of Achaea; upon completion of this traditional Republican magistracy he would be enrolled in the Senate. The inscription omits all mention of a term of service as military tribune; John D. Grainger speculates that Senecio may have served with Legio XXI Rapax, which was destroyed by the Iazyges in 92. He was the emperor's candidate for plebeian tribune and praetor, a clear honor; that the emperor's name is not provided suggests he was Domitian, who suffered damnatio memoriae after his death. After achieving the rank of praetor, Senecio was commissioned legatus or commander of Legio I Minervia. He was then governor of Gallia Belgica for the term 96-98. It was while governor that Senecio provided early support to Trajan. Senecio became consul ordinarius in 99. During the Dacian Wars, he held the governorship of Moesia Superior. Afterwards he earned a second consulate in 107 as well as a statue at state expense.
Personal details
Senecio was a member of literary circles. Pliny the Younger addressed two letters to a "Senecio" who is commonly identified with him. The first, beginning with "This year has produced a healthy crop of poets", is on the health of contemporary Roman literature. The second is a request for a commission as military tribune on behalf of the relative of Pliny's friend Calvisius Rufus. Plutarch also dedicated several of his Parallel Lives as well some of the individual Moralia to Senecio. These include reminisces about Plutarch's and Senecio's conversations at Athens, Patras and Rome, as well as at Plutarch’s home in Boeotia, where Senecio attended the wedding of Plutarch’s son. Senecio married the daughter of Sextus Julius Frontinus, a three-time consul. They had a daughter, Sosia Polla, who married Quintus Pompeius Falco.
