Cervantes' theme throughout Don Quixote is quite consistent and straightforward.  Though Cervantes makes a thinly veiled attempt to keep his biography of the Don objective, the reader quickly realizes that Cervantes sides strongly with his lead character.  Despite the lengthy digressions and numerous episodic adventures, the theme of the novel is clear-the values of the Golden Age of men have been lost over the centuries and must be resurrected for the good of society.  Before the fall of man, when the earth was still a paradise of sorts, Quixote explains to some goat herders, Mother Nature provided all that man needed, making it needless to steal, cheat or lie.  He goes on, "Neither fraud, nor deceit, nor malice had yet interfered with truth and plain dealing." Because the world is no longer in such a state, however, "the order of knight-errantry was instituted to defend maidens, to protect widows, and to rescue orphans and distressed persons," the knight continues.

Quixote's code of knightly conduct is not simply an idle notion, but indeed a life-changing belief-his whole life's mission is to right the wrongs that have befallen his world.  Readers may laugh at his idealized betrayal of lady Dulcinea, but his romanticized vision of courtly love is commendable.  For example, Quixote forbids himself from thinking any impure thoughts about his fantastical princess.  This suggests that the knight-errant, though he obviously feels a certain satisfaction in righting society's wrongs, values his belief in moral justice over his personal pleasure or happiness.

Yet unlike Don Quixote, Cervantes recognizes that reality can no longer accept such ideals of knight-errantry.  Though the Don valiantly strives to carry his Golden Age ideals into the corrupt world of modernity, embodying the virtues of bravery, respect, justice, politeness, loyalty and reverence for God and others, Cervantes must make such outdated ideals a sign of madness.  Only Don Quixote is able to remain constantly moral, while the world around him is constantly immoral.  Indeed the fact that the knight-errant must be thought delusional to possess such morality sheds more light on the his world than on Quixote himself: the Don must be mad in order to remain true to his chivalrous principles.