Shaw's exploration of Joan of Arc is so in-depth that there are many themes examined in his play Saint Joan. Some of them are

• genius and saintliness
• mental superiority causing animosity
• visions and visionary method
• gender and gender dressing
• feminism and a man's life
• youthful immaturity and educational ignorance
• science versus religion

The opening of Shaw's play positions Joan as an "upstart" unafraid of men and man's patriarchal authority over women, while simultaneously showing man's fearsome strength (which can easily be seen as weakness). Captain Robert de Baudricourt is raging because his steward can provide no eggs (and no milk the day before). The steward, cowering, explains the loss of food is due to the presence of the maid: "The girl from Lorraine, sir. From Domrémy." According to the steward, the maid is so potent in person, so "positive," that she can influence the hens to stop laying and the cows to stop giving milk. This introduction of Joan sets the stage for Shaw's many themes, such as her genius intellect and her religious faith.

Joan, theme of genius: Shaw, in the Preface to his play, says Joan is an "upstart," one who flies in the face of convention to assert his or her own superiority over established leaders. He explains her achievements as being the result of genius. In presenting this theme in the opening dialogue and character interaction, Shaw draws the picture of Joan as an immature, uneducated, rustic, ignorant, captivating girl who can face down military heroes because her intellect is so superior that she sees deeper and more profoundly than they do: "A genius is a person who, seeing farther and probing deeper than other people, has a different set of ethical valuations from theirs" (Shaw, Preface).

Joan, theme of religious faith: The source of Joan's motivation in life was her religious faith in what she held to be Christian truths. It was her unshakable faith that underpinned all her actions and provided the source for her visionary experiences. Accordingly, Shaw made some of her first words the introduction to her religious faith motivation.

JOAN [bobbing a curtsey] Good morning, captain squire. Captain: you are to give me a horse and armor and some soldiers, and send me to the Dauphin. Those are your orders from my Lord. . . My Lord is the King of Heaven.

Shaw draws a picture of the deep faith that will lead Joan to defy convention, lead military leaders to victory, defeat England, attempt perilous escape from imprisonment, and walk to the stake to be burnt even though her final vision from Saint Catherine led her astray. It is this deep faith, which Shaw presents and examines as a significant theme, that enables Joan to accept the religious visions (in much the same way Emperor Constantine accepted religious vision) that lead her to save France.