The title character in the Miguel de Cervantes novel Don Quixote is a man who chooses to see the world through the lens of his ideals rather than settle for the mundane reality of country life.

Don Quixote immerses himself in books of chivalry, admiring the code of honor and bravery they describe. He becomes so preoccupied with the ideals the characters embody that he neglects his duties and his home in favor of contemplating and discussing chivalry. This fascination leads him to reject the reality of his life as an ordinary Spanish landholder and to perceive himself as the ideal knight, championing justice in a troubled world.

…he fancied it was right and requisite, as well for the support of his own honour as for the service of his country, that he should make a knight-errant of himself… righting every kind of wrong, and exposing himself to peril and danger from which, in the issue, he was to reap eternal renown and fame.

Don Quixote does not just transform himself; he reinvents those around him to fit into his ideal world. Because every knight needs a lady to dedicate his deeds to, Don Quixote chooses an attractive farm girl from a neighboring village, Aldonza Lorenzo, to be “Lady of his Thoughts.” He re-christens her with the beatific name Dulcinea del Toboso. The name reflects how he sees her as a saintly, gentle maiden who “is worthy to be lady of the whole universe.” But his neighbor Sancho, a staunch realist, has another view of the young woman.

“I know her well,” said Sancho, “and let me tell you she can fling a crowbar as well as the lustiest lad in all the town… the whoreson wench, what sting she has and what a voice! I can tell you one day she posted herself on the top of the belfry of the village to call some labourers of theirs that were in a ploughed field of her father’s, and though they were better than half a league off they heard her as well as if they were at the foot of the tower; and the best of her is that she is not a bit prudish…”

If Aldonza/Dulcinea is not the saint Don Quixote sees, Sancho also does not achieve the standard of perfect squire. He is not noble or educated, nor is he dedicated to serving his knight. He is a laborer on a nearby farm, who only agrees to accompany Don Quixote after being promised the position of governor over any islands they conquer in their adventures. Even Sancho’s appearance is ridiculous. Instead of a horse, he rides a donkey, the only animal he can procure.

… he meant to take also a very good ass he had, as he was not much given to going on foot. About the ass, Don Quixote hesitated a little, trying whether he could call to mind any knight-errant taking with him an esquire mounted on ass-back… For all that, however, he determined to take him, intending to furnish him with a more honourable mount when a chance of it presented itself, by appropriating the horse of the first discourteous knight he encountered.

Don Quixote’s hesitation over Sancho riding the donkey reveals that he is not completely divorced from reality. He knows that this picture is not right, but he does not allow that to dissuade him. He ignores reality, telling himself that he can soon elevate this coarse truth to his ideals. He chooses self-delusion in his perception of Sancho, in his view of Aldonza, and even in the self-image he insists on.

Because Don Quixote finds the world around him to be lacking in honor and chivalry compared to the romances he is addicted to reading, he is driven to create his own reality. He manufactures an imaginative, ideal world for himself out of the more prosaic stuff of reality all around him. In his own mind, he is a knight errant, on a mission to protect and save society. This gives him an illusion of control sadly lacking in his life.

When he decides an inn is a castle, this idealization of the ordinary makes him happy, but the reality of the situation is that people think he is crazy and beat him up.

In his self-created, ideal world, the knight Don Quixote wanders the countryside of Spain so desperate for a cause, so in need of a fearsome enemy, that he mistakes windmills for giants. Feeling it is his mission to bravely and boldly protect those around him, he famously tilts at the windmills. Ideally, in doing so he is displaying his courage and fulfilling his duty as a knight. Realistically, he accomplishes nothing and brings physical pain to himself.

People have long debated this book and the relationship of the ideal to the real. What is the cost of attempting to create the ideal world we desire, of being the change we want to see? Is it worth the price? Where and when do we make our compromises with reality? 

Don Quixote is a well-loved and admired "classic" tale. The self-styled hero, Don Quixote, is close to madness, having "dried out his brain," and is of the belief that he is as good as any knight in serving and protecting his lady love and her honor. The details are not important to him and he is not discouraged by the less than ideal location of La Mancha, or circumstances or his romantic notions and, as the plot develops, he becomes certain that any misfortune is the work of a wizard by whom he is cursed. Don Quixote is is neither affected nor aware of his own insanity. Chivalry is all that is important in his quest. 

The best example of the idealism versus realism concept is Don Quixote and his squire, Sancho Panza and their unlikely relationship; it is at times destructive in nature and unfortunate but at other times reassuring. It is the combination of their different outlooks which drives the story and which makes both characters more believable. Sancho feels pain and has no intention of concealing this fact, regardless of what he sees Don Quixote do in the interests of bravery, feigned or real. The reader can appreciate Don Quixote's idealized version more readily when he accepts the need to view things from a different angle and a more positive perspective. Furthermore, the fact that the men know that they are characters in a story and that the story depends on their actions ensures that the reality becomes intermingled with the fantasy and the characters are not always sure which is which.

Don Quixote's "love" for Dulcinea, apart from being comical, adds to the subjectivity of any encounter or reality. To him, she is beautiful and mysterious, not remotely like the real peasant woman on whom he has based his illusion. There is a fine line between Quixote's appearance as a fool and his hero status as he immerses himself in his fantasies to avoid his dismal and discouraging reality. The fact that, towards the end, his madness will subside and his death will follow reveals that, for Don Quixote, the ideal gives him purpose and brings meaning to his life and, without it, there is no reality, only death. 

Idealism is the "ideal" perfect situation. Realism is "reality"--how the world really is.

One obvious example of idealism is how Don Quixote believes himself to be a knight.  In reality, he is a skinny old man riding a malnourished old horse around the countryside.

He also chooses a "lovely" young lady in whose name he does all his grand deeds.  In reality, she has no clue he's doing this.

He fights a "dragon" to rescue the damsel.  In reality, the dragon is a windmill.