Veil as symbol of purity
The veil separates women from men's sight while they are out in public. One of Usbek's eunuchs' duties is to protect his wives from the sight of other men, lest they be contaminated by it. Usbek and the eunuchs believe that they are helping the women stay "pure". The fact that Zelis accidentally lets her veil slip one day is, to Solim, a sign of unforgivable moral looseness.
Seraglio as allegory for kingdom
Usbek is the unquestioned ruler of the seraglio much as the aging King is the unquestioned ruler of France. Like the French king, Usbek has employees and other people to whom he delegates authority. However, given that Usbek expresses a preference for fair, honest, virtuous leadership as opposed to vicious authoritarianism, he runs his own household first as an absentee and then as a savage dictator.
Philosopher's Stone as a symbol of futility
The Philosopher's Stone, supposedly a substance that allows its owner the power to magically turn lead into gold, does not really exist. Most relatively educated people, even in the 1700s, were aware of this fact since they had come to embrace science as a way of finding out about the world. The alchemist's obsession with the Philosopher's Stone, and his habit of bankrupting himself and others in the quest for it, symbolizes the futile search for unscientific sources of wisdom and power.
Travel as metaphor for exile and growth
Traveling to another land has a different meaning for each of the Persian characters. To Usbek it is part of a self-imposed exile: when he left Isfahan, he was fleeing for his life. He sees the new nation of France as a poor substitute for what he has left, and is more critical of it. Although he likes at least some of what he sees, for the most part he misses Isfahan and his family.
To Rica, travel is a metaphor for growth and adventure. He explores France and Italy, meeting new people and encountering new ideas. When Usbek wishes to return to Isfahan, Rica does not. To him, travel is not a process of moving away from something dangerous but of moving toward something interesting.
