Following his service to the Vulcan High Command by 2165 Soreth lived in ShiKahr and frequented a debate house located in the city's business district. Soreth initially opposed Vulcan's participation in the United Federation of Planets and spoke in defense of the High Command when the authenticity of the Kir'Shara was cast into doubt due to the apparent resurfacing of another Kir'Shara that contained writings making it appear that the beliefs of Surak were in line with the beliefs of the High Command and people like former administrator V'Las.
A group of Vulcans loyal to V'Las soon began making plans to seize power via a coup d'état. However Admiral Jonathan Archer and Captain T'Pol along with the crew of the USS Endeavour and Vulcan Security were able to stop the coup and recover the real Kir'Shara which Archer and T'Pau had uncovered over a decade before. They also uncovered proof that the duplicate Kir'Shara was a fake designed to cause discord in Vulcan society so that it would be easier for V'Las to take over.
Following these events Soreth felt quite embarrassed to have supported V'Las, finally realizing that V'Las had never had Vulcan's best interest at heart, but instead was acting to conquer Vulcan for himself. Soreth realized that the self styled champion of Vulcan purity and logic had turned out to be just as emotional and erratic as any human or Andorian. Soreth also observed that the Federation had allowed Vulcan to settle these matters internally instead of increasing their presence on Vulcan. Due to these factors Soreth decided that he would no longer oppose the Federation. He also allowed that perhaps mind melding was not neurologically harmful, but still felt it was uncouth and reckless to engage in melding with others. Soreth resolutely continued to the debate house to share his new insights with the other regulars of that particular debate house. (ENT - Rise of the Federation novel: Uncertain Logic)
Soreth eventually entered into the service of the Federation government. By the 2270s, Soreth was serving as a Federation Commissioner. Soreth was sent to the Lorina colony on Daran IV to serve as a Federation observer and adviser to Natira and the Fabrini. During this time Soreth engaged in verbal sparring with Spock, hoping to provoke the man into an emotional response to show that Spock's work to integrate some measure of emotion into his life was misguided at best and dangerous at worst. Dr. Leonard McCoy harbored a dislike of the man, nicknaming him Sorehead.
He endorsed a purely secular society for the Fabrini, and encouraged them to totally reject the religious traditions of their ancestors. When the Fabrini realized that the only way to stop the strife in their society was to balance their secular and religious traditions, Natira and Rishala requested a different representative. Soreth agreed to step down, and subsequently returned to Federation space on board the USS Enterprise. (TOS novel: Ex Machina)