Absolutely everyone has delusions, everyone. The measure of how debilitating a delusion is comes from how well one functions. I can think of three classic examples from the later period of the Hundred Years War (which lasted 116 years). Charles VI of France was the king from 1380 until his death in 1422. He believed he was made of glass, and had servants strap him up each day so that he would not inadvertently bump into something and shatter. He was not competent to rule, and early on, his brother Louis, the Duke of Orléans ruled in his stead. Their first cousin, Jean sans peur (Fearless John) wanted a slice of the pie, and hated Louis, and had him murdered in 1407. John and Louis weren't terribly deluded, just the run of the mill delusions of their age. But John's big delusion was that he was loved by the people of France and that they wanted him to rule. That was part of the reason he had Louis murdered. The people of France wanted no part of him. In 1413, John, who was the Duke of Burgundy and richer than Charles, invaded France. The French didn't have much use for the Burgundians, either. In 1414, one of the King's sons, the Duke of Bourbon, lead an army out to drive the Burgundians from France. When they reached Soissons, even thought the Soissonais were loyal subjects, Bourbon "gave the city up to the sack" when they took it back from Burgundy. For three nights and two days, the French army plundered, raped and murdered. I won't go into the ugly details.
In England, in 1413, Henry V Plantagenet became King when his father died. Henry was seriously deluded. His great grandfather, Edward III, had started the Hundred Years War, as a pretext to protect the land he had in France and reclaim some of the land in France that his great, great, great grandfather, Henry II had once had in France. Edward never really though he'd be the King of France (he had a dubious claim), but he wanted to use the war to take land in France. Nobody in France wanted the King of England to be the King of France, and Edward knew that.
But the delusion of Henry V was that he was
the King of France, and that the French were denying him his rights. He was a religious fanatic, so the first thing he did was round and hang or burn heretics, to get right with god. But Henry was competent. As the English of the day said, King Charles had porridge for brains, but Henry had brains for brains. Religious fanaticism was much more tolerated then than it is now. In 1415, Henry invaded France, and after a particularly nasty spate of religious delusion, found himself with an army of only about 6000 or 7000 men facing a Franco-Burgundian army of 25,000 to 30,000 men (they had kissed and made up). Shakespeare tells us that Henry told his men "Today is St. Crispin's day." He probably did--remember, he thought he was on a mission from god. St. Crispin and his brother St. Crispinian were the patron saints of the city of Sossions. Henry was telling his little army that they would be the instrument of god's vengeance on the French and Burgundians. Then a miracle occurred, which is to say, the French screwed up again. Henry defeated them, killing more than 4000 outright and taking more than 2000 prisoners (they only kept the ones who could pay a ransom). Of course, Henry was more convinced than ever that he was on a mission from god, and the times being what they were, Europe agreed with him. How else could a foot-sore, starving little army like that defeat the chivalric might of France and Burgundy.
Henry finally cornered Charles and forced him to sign a treaty. Henry married his daughter Catherine (who promptly provided him a son) and Charles agreed that when he, Charles, died, Henry would become the King of France. But when Henry's son was just nine months old, Henry died of a camp fever in 1422, while Charles was still alive, although not for long. Charles' son Charles, the dauphin, claimed the treaty was void, and that he was now King. The dauphin was no saint, he had had John the Fearless of Burgundy assassinated in 1419, which was a stupid move because now Phillip the Good of Burgundy became an ally of England.
Henry VI was still just a boy when the English laid siege to the city of Orléans in 1428. Charles the Dauphin was at Chinon, to the south and east. Early in 1429, a peasant girl from Lorraine, Jeanne d'Arc, rode into town, and announced that she was on a mission from god. Stes. Catherine and Margaret and the Archangel Michael had sent her to liberate Orléans and see the Dauphin crowned. In the 15th century, if you said that the saints and angels talked to you, people thought that was reasonable. They might quibble over the meaning of the message, or suggest that maybe Satan had deceived you, but no one automatically assumed that you were crazy (if they did, they kept it to themselves). The Dauphin was not having a great war, which i suspect is the main reason he decided to give Jeanne a try. He had her given an expensive suit of armor, and the ladies of the court embroidered an elaborate banner for her, and off she went to Orléans to lift the siege.
The English went too far. They didn't tell their men that Jeanne was deceived by Satan, they told them that she was a willing tool of Satan, that she was a limb of Satan. Jeanne actually had some native military talent. She also had the fervor of the truly deluded. She convinced the Duke of Alençon that they should attack Les Tourelles, a double barbican fortress at the south end of the bridge leading into Orléans. It was a bold plan, and brilliant, if you could pull it off in one day, before the English army could cross the river to save the fortress. Alençon was the titular commander of the army, you can't have a mere peasant leading the army. The real commander, though, was Jean d'Orléans, Dunois, bâtard d'Orléans
, Bastard of Orléans, the bastard son of Louis who had been killed in Paris in 1407. He was skeptical, but he went along with the plan, convinced that it wouldn't work.
Jeanne lead the French to the attack, and while she was climbing a scaling ladder, she was hit by a quarrel from a crossbow, and knocked off the ladder, landing on her back in the ditch. The English were jubilant, they had killed Satan's plaything. The French were correspondingly downcast--Jeanne must not have been on a mission from god. Dunois, the Bastard, was in an "I told you so mood," an ordered the army to retreat in the morning. Jeanne was not dead, she had just been stunned. That good armor that the Dauphin had bought her preserved her life. She insisted that her armorer re-arm her, and that she be helped into the saddle.
Most of the French army, like the English, thought she had been killed. When Jeanne road through the camp, they went crazy. God had preserved her, had raised her from the dead! They became wild men and rushed to the attack. The English were now cast down. They saw Jeanne riding at the head of the French, and thought that Satan has raised her from the dead. They thought the limb of Satan was coming to dance them down to Hell. Most of them threw down their arms and tried to escape. Dunois was skeptical, but he wasn't stupid. He had horsemen on either flank, and they rode down the English who tried to escape. Jeanne had kept her first promise, and now everyone believed in her. Had not god raised her to lead the French to victory? Jeanne remained with the army as they drove the English from the Loire valley, and she was there at Reims when Charles VII was formally crowned the King of France.
The rest of Jeanne's brief life was, of course, tragic. But even then, she kept her head. Cauchon, the president of the kangeroo court that tried her would attempt to trip her up, and she would just reply "You
say so." He once casually asked her if the Archangel Michael was naked when he appeared to her. She just laughed and asked him if he thought god could not afford to clothe his saints and angels.
In an age of delusion there were three important figures who were notably deluded. Charles VI was not competent to rule France, and it caused almost a half century of misery and heartache for the French. Henry was deluded and thought he was on a mission from god. While he lived, all the evidence was that he was correct, and Europe agreed. Jeanne was deluded, but she accomplished her mission, and, eventually, all of Europe agreed that she had been the messenger of god.
The only measure of delusion is whether or not the deluded individual can function effectively. The only judgment of history is whether they did good or ill.