- "Yeah, and you've discovered the importance of higher beings. Celebrities... like me, as people who worship and guide you to truth."
- ―Jimmy Boston
Exercising the Truth is a Strangers and Freaks mission in Grand Theft Auto V, given to protagonist Michael De Santa by the Epsilon Program. This mission is the penultimate mission in The Truth mission series.
The mission begins at an unnamed collection of mobile homes in the western half of the Grand Senora Desert, just north of Harmony. The location is not immediately marked on the game map but will appear once Michael enters the Desert area. In the enhanced version, the location is always marked on the map. Additionally, Michael must wear his Epsilon uniform for the mission to start.
At the location, Michael meets Marnie Allen, Jimmy Boston, and Tom. The three are pleased with his progress and Jimmy awards Michael a medal for his efforts. At that point, Cris Formage, the leader of the Epsilon Program, speaks over a nearby loudspeaker and also congratulates Michael. Cris tells Michael that Michael is very near to enlightenment. When Cris's message ends, Marnie tells Michael that next he must deliver a large donation to the Epsilon Program headquarters in Rockford Hills. But first, he must run five miles through the desert.
The three Epsilon members leave. Michael must then travel five miles on foot throughout the Grand Senora Desert. At each tenth of a mile, a message will display above the radar, showing the player the distance Michael has walked or run. If Michael leaves the desert, the count will reset and the player must start over. Within these limitations, Michael can do anything within the Grand Senora Desert's borders, including visit towns, shop at stores, commit crimes, gain and lose wanted levels and so on. Watch out for dogs and cougars as they may attack Michael, wasting him instantly and resetting the progress.
Upon reaching four miles, Michael receives a call from Cris, telling Michael that he is nearly finished. At five miles, Cris calls Michael again and congratulates him. Michael asks if he is done, Cris explains that his journey has only began and that he must now deliver the large donation to the Epsilon center. After some time passes, the final Epsilon mission pops up on the map.
- Both the PS3 and Xbox 360 have a glitch in which Formage does not call Michael the first time until after Michael has completed all five miles, with the follow-up call arriving immediately after, though this is rare. This can also happen on the Xbox One and PS4 versions, with Michael hanging up on Cris. This is fixed by simply waiting a minute or two and the call will come through again.
- Hayden Dubose - "I'm sure I must be mistaken but I was out bird watching in the Senora Desert and I could have sworn I saw you running around in what looked like a pale blue space suit?"
- If By the Book starts while running the player's pilgrimage, it does not interrupt it. If you choose to complete the pilgrimage first, the calls from Cris will not come until the Story Mission is completed.