Dixon's steadfast spirit

[Terrance]

Dixon is Cheerfully confident, optimistic, playful, good humored, or as
Mason describes him, "the unwavering Larrk of the Sanguine." 247  How
did he come to be so? Well, it's his disposition just as Mason's is
rather gloomy, but I think the argument can be supported, with examples
from the text, that Dixon is also an unwavering man of the spirit and
this is consistent with his unwavering concomitant playful good humor. 
The opposite is the case with Mason. 

It's not that Dixon doesn't get angry or upset at the folly and
brutality he sees or that he lacks conviction, quite the contrary, but
his unwavering spirit (of the Larrk and Quaker) is  a constructive
humor/humor that allows him to live in the world with Grace. 

I think it makes sense that P needs an unwavering character of such
humor/humor and spirit in this novel. 
Dixon, I think, is such a character.