Church is the groups main pilot and engineer. Not only is the Roger Young his ship, but it is actually part of him.
During a past heist that went majorly south, Church was forced to repair the central core of the Young using the only operating system he had to hand. His own mind.
As a result his mind is fragmented with logic and reason embedded in the Young, and remaining within him.
Gideon constructed the equilibrium device that allows Church's mind to be whole while plugged into the ship. When unplugged he acts on raw instinct and emotion.