Final answer:
Voltaire likely used the tree as a metaphor to symbolically express Enlightenment ideals, emphasizing the nurturing of individual liberty and reason.
Step-by-step explanation:
Voltaire's purpose for including the example of the "tree" in his essay was likely to illustrate Enlightenment ideals in a symbolic way. As a prominent figure within the Enlightenment, Voltaire was an especially vigorous advocate of intrinsic rights and freedoms, challenging established institutions like the Catholic Church and the monarchy.
His inclusion of metaphors or illustrative examples like the tree could serve to make complex ideas about personal liberty, reason, and the natural order more tangible and relatable to his readers. By doing so, he emphasized the importance of nurturing individual enlightenment, much as one would care for a tree, allowing it to grow and flourish.