In the book, Don Quixote, an old man in the 16th century became obsessed with tales of chivalry and knight-errantry. He eventually abandoned his family and his estate to pursue his delusion of being a knight, vanquishing evil and winning the love of his lady. In truth knighthood in the medieval sense had died out long before, and Don Quixote was embracing a culture that was extinct. At the end of his life he renounced his oath of knighthood and came to his senses, realizing that he had been completely mad.
Don Quixote had an estate and a small family, along with a few friends. Locked away in his library he devoured book after book on chivalry until he was totally obsessed. He eventually resolved to leave his family and his property to become a knight, and travel around righting wrongs to win the love of his lady. In truth he hardly knew this woman, who was simply a local farm-girl. He gallivanted off in search of someone to dub him a knight. He eventually found himself at an inn, which he saw as a castle, and was dubbed by the innkeeper who was just playing along. What followed were a series of misadventures in which Don Quixote went about trying to destroy what he thought were villains, but in truth were just normal people and objects. Perhaps most famous is the case of the tilting at windmills, in which Don Quixote charged at what he thought were giants, but turned out to be windmills.
Don Quixote lured a peasant, Sancho Panza, to be his squire with promises of wealth and fortune. Sancho also abandoned his family, breaking his obligation to his wife an children. Eventually it seemed as though Sancho was just as mad as Don Quixote, playing along with his flights of fancy to such an extent that it seemed impossible to think otherwise.
Don Quixote’s oath of knighthood was at odds with the oath of his state of life, that is, as the head of his household. On his deathbed, Don Quixote finally realized that the books of chivalry he had once been enthralled by were nonsense and a waste of time. He realized that he had wasted the latter half of his life pursuing ridiculous dreams. He renounced his knight-errant oath and re-embraced the original oath that he had abandoned. It was almost too late, but he finally realized the errors of his ways.