In the Garden of Eden (starting at the left), the first “downward slope” drawn is the lake, where Eve first sees herself in Book 4. Though Eve may be part of paradise and created sufficient to stand, she shows signs of fallen qualities–those of our own–from the first time we see her. In Eve’s very first presence she has “unexperienced thought” (4.457) and becomes attracted to her own reflection in the lack by “vain desire” (4.466). She describes her reflection to have “returnd as soon with answering looks” (4.464, emphasis added) where this experience gives her answers of knowledge. Attributing this desire and curiosity of herself should not be characterized as narcissism; unlike Satan, upon the instruction that her “vain desire”(4.66) is unrighteous, she walks away. However, it is worthy to note that her curiosity leads her to conventionally sinful behavior. Her instincts are not to follow good, but to follow knowledge of herself. Even in paradise, she feels incomplete as the limits on her self-exploration limit her knowledge and understanding of the universe.
Following this in the picture, Eve comes across the apple, as stems from Satan at the bottom left. Eating the apple evokes in Eve the sense that she is knowledgeable and superior, no longer fearing death and now with “opened eyes, new hopes, [and] new joys” (IX.985). However, the apple does not provide her any new sense of knowledge besides the experience of doing evil. As she has been tricked by Satan, she has no choice but to follow the pathway downward. The staircase here consists of seven steps, each representing the seven deadly sins Eve follows directly after eating the apple.
In the drawing, the passage then forks into two options: the ability to recognize sins and work toward a new sort of paradise, or continuing following Satan’s path in hell. In Book 3, God decrees how the fallen are to be reprimanded—justice for the fallen was not an afterthought, it was built into God’s original creation of humanity. The fallen are, as God says, “[a]uthors to themselves in all / Both what they judge and what they choose” (3.122-3). For humanity, “[m]an falls deceived / By th’ other first: Man therefore shall find grace, the other none” (12.130-2). Unlike the reprobation of Satan, they can choose to find grace. In the image, Satan does not have any pathway to travel back upwards, he is permanently outcast from Heaven. The humans, in contrast, remain free to choose their fate (they were “formed … free and free they must remain” [12.124]), and so they are given the opportunity to “leave this Paradise, … possess[ing] a Paradise within thee, happier far” (12.586-7). This fall may not have been necessary for them to reach Heaven, but ultimately it was beneficial and they’re “happier farr” (12.587) than before. They now have this Tree of Knowledge to guide them, and they can use this spiritual transformation to choose their path: either continuing down the dark, black pathway and follow Satan (traced along the bottom of the page), or to work their way upwards. While she may reach a different sort of paradise than before, it is far more colorful and she is more in tune, knowledgeable, and satisfied with her surroundings than before.