Dante's Inferno (by Dante Alighieri) illustrates the use of both reason and faith as one travels through life. Although Dante (the character) sees reason as being important, he finds faith far more necessary. Virgil, one of Dante's guides, represents reason. It is his reason that Dante abandons him for another guide, Beatrice (given her knowledge lies in faith in God).
Dante, when defining why sinners did what they did, believes that people use reason to justify their desires (lust, gluttony, incontinence). One example of this thought is found in Canto 5 (lines 38-39): "because they sinned within the flesh, / subjecting reason to the rule of lust." According to Dante, a person's need to reason his or her behaviors proves that reason can manipulate mankind.
In each canto, different sinners are defined. Given that each have alternative thoughts regarding the importance of God, each used their own reasoning skills to define what they believed to be most important. For example, in Canto 5, the heretics are in the sixth circle of hell because they used reason to support their own belief that happiness existed where pain did not.
Figuratively, the symbolism of Virgil representing reason and leading Dante through hell illustrates Dante's (meaning mankind's) support on reason although it can manipulate him (mankind as a whole) at points.