Idealistically, hell is a place for the truly sinful, and Heaven is a place for martyrs and saints. Where do those who sinned but began repentance belong? there must be a bridge between the two, otherwise, there would be no motivation to follow a path of righteousness, if a spot in Heaven was guaranteed to sinners who uttered a breath of repentance. To create an intermediary place for repentance seemed logical. However, until Purgatory such a place did not exist in literature.
In a style much differentfrom what one has seen in Inferno, Dante begins Purgatory, the second canticle of the Divine Comedy, with an atmosphere of hope and light. "For better waters, now, the little bark of my poetic powers hoists its sials, and leaves behind that crulest of seas," (lines 1-3). Gone are the pitiful shades suffering their cruel torments that so haunted Dante's every step in Hell. However, despite the dissimilarity with Inferno in mood and atmosphere, Purgatory shares a moral structure much like that of Inferno. This helps to advance the story of the pilgrim's journey towards salvation, while giving the reader an idea of what to expect in Purgatory.
Whereas souls were dropped into Hell, modeling Lucifer's fall, the souls delivered to Purgatory encounter a cliff that separates Ante-Purgatory, the region of the late repentant, from Purgatory Proper. From there, they must ascend the mountain, which is divided into seven circles, or terraces, each devoted to one of the seven deadly sins. the severity of the sin is in direct proprotion to its location on the Mountain of Purgatory. Worse sins, such as pride or envy, are placed at the beginning of Purgatory proper, and thus closer to Hell. Lesser sins, like that of lust, are positioned at the top of the mountain. This remids one of the similar structure in Inferno; there, sins were also organized according to severity, though with the least severe sins first, and the worst last.
