What is the role of imagination in Don Quixote?

Don Quixote becomes obsessed with the idea of knight-errantry to the point of losing himself. His loss of reason is similar to that of any person who becomes obsessed with something. As he says to his niece, "if these knightly thoughts did not monopolize all my faculties, there would be nothing I could not do...."

Indeed, Don Quixote never quite loses his mind, he simply indulges—to the fullest extent— his imagination. It is a conscious effort, "and that is where the subtleness of my plan comes in. A knight-errant who goes mad for a good reason deserves no credit; the whole point consists in going crazy without cause." That is, if knight-errantry were in fashion, Don Quixote would not be unique. If he succeeds in resuscitating chivalry, he will become famous.

The point of Don Quixote's knight-errantry is to make a fantasy come true. Living a fantasy even for a short time is more than most hidalgos could say. His friends unwittingly bring his wish to fruition better than he could have possibly hoped. Everyone wins, for "what the world needed most of all was plenty of knights-errant" and by acting in his fantasy, his friends help revive the traditions of knight-errantry.

In fact, it is their indulgence—their cooperation with the fantasy—that fulfills Don Quixote's dream and "astonished [him], and for the first time he felt thoroughly convinced that he was a knighterrant in fact and not in imagination." Don Quixote's madness, sadly, is the only way for adults to play in the serious world of Spain's Golden Age.