While there's a lot be confused about with Guyon, the Palmer, his advisor, is more clear-cut. The Palmer is a pilgrim, someone who has made a trip to the Holy Land to show his piety and religious devotion. Essentially, he's got a lot of Holy-cred.
But what he also has is some serious brains, since throughout Book 2 the Palmer functions as an embodiment of reason and rationality and how true religious devotion must always be coupled with rationality. He's always telling Guyon the right thing to pursue, what to avoid, and how best to think of things.
Sometimes, he and Guyon are so inseparable, that the Palmer seems to function almost as a outside representation of Guyon's internal thoughts. It's no wonder than that as soon as Guyon and the Palmer are separated, things go a bit worse for Guyon: he's back to making mistakes, fainting, and other embarrassing missteps.
The Palmer's status as a religious leader is also established through his use of his handy staff, with which he even calms the ocean, an action very reminiscent of another holy leader dude: Moses.