It seems to be the ongoing debate within the world of Spanish liturature: is Miguel Cervantes' Don Quijote crazy or sane? He is certainly an ambivalent character, and manages to keep the reader guessing with every action that makes one go, "huh?!" Yet, for every action that suggests Don Quijote's lunacy, he also has his moments of philosophical genius. For example, I just read Chapter 11, where Don Quijote is spending time with a group of simple goatherds. During the course of their dinner, Don Quijote makes a long speech deliberating the good will of men. He referred to times far gone, when people and things did good for the sake of doing good and asked for no payment or reward in return. He was also extremely grateful and, I think, impressed at how the goatherds had only met him briefly and yet did not hesitate to invite him to share their meal.
That chapter is only one of what I am sure is many instances where Don Quijote shows a philosophical side that leagues of people lack today. I am not sure that I can prove his complete sanity and mental health, however, I do not believe he is one-hundred percent crazy.