During the Age of Doubt, 2525 by the UNSC calendar, Truth was known as the Minister of Fortitude. He had gained his standing during a stint as junior staffer in the Ministry of Concert. At that time, he unearthed a conspiracy by several Kig-Yar ship captains to poison several recreational narcotics often enjoyed by Unggoy, rendering them infertile, and serving as petty revenge for the displacement of Kig-Yar nests caused by a recent Unggoy overpopulation. Despite Fortitude's warnings, the matter was ignored and soon escalated into a bloody skirmish known as the Grunt Rebellion.
Fortitude found himself involved in a conspiracy when the Vice Minister of Tranquility, later known as the Prophet of Regret, informed him of the massive trove of "Forerunner artifacts" (which was actually the human population ofHarvest) that a Luminary had discovered on that planet. Tranquility planned to use these artifacts to spring himself into a position of high power, as a Hierarch of the Covenant, and offered the same for Fortitude. This marked the first alliance between the Prophets and the Jiralhanae, as Tranquility wisely decided to use them to retrieve these artifacts, rather than upset the fine balance of power by allowing the Sangheili to gain the treasures.
In order to push the three current Hierarchs, Tolerance, Obligation and Restraint from their positions, Fortitude utilized blackmail against the Prophet of Restraint. Tranquility had shown himself as a sympathizer for those blacklisted from reproducing due to inborn genes, after being urged to do so by Fortitude who was aware that Restraint had illegitimately fathered two children. The Prophet of Restraint offered Tranquility a high position if he would adopt the children, but the scheming Prophets instead used this to their advantage, blackmailing him and forcing the Prophet to step down or have his scandalous affair made public.
Before their coup, the Prophets visited an "Oracle" within the Forerunner Dreadnought, an ancient AI known as 05-032 Mendicant Bias, that had stored itself in the ship and had not spoken for several hundred years. When the Luminations of Harvest were inserted into its matrix, it suddenly reactivated and revealed that the symbols had been misinterpreted - that Humans stood as equals to the Forerunners, that the hallowed "Reclamation" glyph actually meant "Reclaimer," and that the Covenant had been mistaken in their beliefs that all of the Forerunners had transcended when they initiated the Great Journey. This was a massive revelation with great implications for the whole Covenant: If humans were the chosen successors of the Forerunners (or were surviving Forerunners themselves) yet had not transcended when the Sacred Rings were last activated, then that meant that the Halos would not necessarily provide godhood to all who walked the divine path. This knowledge, if revealed to the masses of Covenant followers, would lead to revolt, the collapse of the entire Covenant Hierarchy, and the Prophets being deposed as divine leaders; the Prophets' age-old promise was that none would be left behind when the Great Journey began.
The Oracle tried to launch the Dreadnought from High Charity to find and bring the humans to The Ark, but before it could succeed, the Lekgolo worms that were tasked with exploring the Dreadnought's inner regions short-circuited the connection, and the two co-conspirators, along with the Philologist (leader of the ascetic priests and later the Prophet of Mercy), disconnected the Oracle from the ship. When Fortitude realized the implications of what the Oracle had told them, he and the other two Hierarchs-to-be agreed not to tell the masses of their discovery and decided that the humans must be eradicated once and for all before any of the Covenant could learn the truth.
The three Prophets successfully implemented their plan and became the new rulers of the Covenant which heralded the beginning of the Ninth Age of Reclamation. Fortitude chose the name "Truth" as a reminder to himself of the truths he must never tell and the lies he would have to spin in order to prevent the Covenant from fragmenting.