People in 15th century Europe believed that other people did hear voices, and did not consider it a sign of mental illness. They might or might not consider such a person delusional, but they might consider such a person to have been deluded by Satan, rather than deluded in a mental health sense. I’ll comment further on that in a moment.
It was widely believed at the time that she had told Robert de Baudricourt about the English victory at Rouvray several days before the news of the event reached Vaucouleurs, Baudricourt’s headquarters. We can’t know for certain about much concerning her brief career because most accounts were written 50 or 60 years after her death in 1431. The best evidence we have about her comes from her two trials. The first was, of course, the trial which condemned her in 1431. The second, of which most people are unaware, reached a verdict 25 years after her death, and is called the trial of rehabilitation, and found that Cauchon, her judge, had acted in an heretical manner and had acted for secular and venal reasons. At the second trial, people who had known her personally testified to her piety and character, and several military men who had served with her testified to her courage and military sagacity—while members of the first court who were questioned were less than forthcoming and seemed to suffer from frequent lapses of memory.
Joan’s greatest victory came at the beginning of her military career, when she lifted the siege of Orléans. No French army would be commanded by anyone but a high ranking nobleman, and the nominal commander of the army at Orléans was the Duke of Alençon. But the actual commander, the operational commander was Dunois. Jean d’Orléans, John of Orleans, also known as le Bâtard d’Orléans—the Bastard of Orléans was the bastard son of the former Duke of Orléans, Louis, who had been murdered by agents of the Duke of Burgundy in Paris twenty years ealier.
Dunois had taken the Anglo-Burgundian strongholds along the south bank of the River Loire opposite Orléans in the preceding weeks, all but Les Tourelles, a double barbican fortress at south end of the bridge into Orléans. He did not want to attack les Tourelles as he thought it would be too costly. However, he was overruled by the Duke of Alençon, who had come to believe that Joan was divinely inspired (as he testified himself). On May 7, 1429, the French went to the assault enthusiastically, but Joan was wounded by an arrow (some people claimed a quarrel from an arbalest, a heavy duty crossbow) while standing in the ditch beneath the walls—some people claimed she was shot while mounting a scaling ladder. You can see the problems arising from conflicting testimony. She was carried away and the French lost heart and fell back. The English were jubilant. As i mentioned earlier, people in the 15th century might believe she was deluded, that she had been tricked by Satan. The English commanders had taken it a step further and told their soldiers that she was a willing limb of Satan. With the French discouraged, Dunois, in an “I told you so” mood, ordered the retreat of the army. When Joan herd of this, she called for her horse, and insisted on riding back to the assault. Now the French were jubilant. They had thought her dead or dying, and now she was leading them to the attack again. The English were correspondingly dejected—they thought the limb of Satan had come to dance them down to Hell. If Joan was deluded, she lived in a deluded age. Many of the English attempted to escape the fortress, and most took no more steps to defend les Tourelles. With the fortress taken, and a sure path into the city secured, the overall English commander, Talbot, decided to pull out the next day, so that the French did not take his fortified camps one by one. The siege of Orléans was lifted, and those who had doubted Joan were now convinced, or at least remained silent.
Attacking les Tourelles was really a brilliant military decision, even though it was taking a big risk. Cut off from the other English forces by the river, no one could come to their aid, at least not immediately. It was a bold gamble that paid off with a greater success than anyone had anticipated. Whether or not the idea was original with Joan—and witnesses at the second trial said that it was, including her banneret, the man who usually carried her banner into battle—and the Duke of Alençon. In an age when noblemen despised peasants, and Joan was a peasant, that is powerful testimony.
This first trial was a frame-up, a kangaroo court. But even there, Joan showed herself to be intelligent, even if uneducated and functionally illiterate (she could sign her name, and that was about it), she was as canny as peasants are often claimed to be. When Cauchon asked her if the archangel Michael was naked when he appeared to her, she laughed and asked him if he thought God could not afford to clothe his saints and angels. When anyone asked a loaded question, her standard response was “You say so.” In the end, they convicted her not of heresy, or of witchcraft (which many people today believe), but of defiance of the Church Militant. The Church Triumphant was the church in heaven,and the Church Militant was the church on Earth. Their evidence was that she had worn men’s clothing. Even that was rigged—first because St. Augustine of Hippo had decreed more that a thousand years earlier that a woman could wear men’s clothing in order to protect her virtue. Second, because on the morning she was executed, she awoke to find that the woman’s clothing she had been wearing had been removed, and had been replaced with the men’s clothing she had been wearing when she had been captured by the Burgundians. The evidence for that is her statement in open court to that effect, which no one contradicted, before she was condemned and taken out to the place of execution.
If Joan was deluded, it certainly did not affect her military judgment or her native intelligence.