According to William Franke, "the basic philosophical implications of the Inferno are that Satan, representing evil, is the center of gravity, and because of this all humans are naturally drawn to him. God, representing perfect salvation, resides beyond the highest sphere of heaven in the Empyrean, and is the most difficult thing in the universe to reach. The three beasts eternally block the right path: The leopard of treachery, the lion of violence, and the she-wolf of incontinence" (Franke, 2013). The author is saying that these creatures represent their respective sins, and that they block the right path for all souls residing on the earth. The fact that the right path is vacant tells us that no man is capable of right living, and so the journey through the inferno is necessary.
Each circle in the inferno is a different level of sins. As Dante travels though the circles he comes to the second where the souls trapped there are essentially stuck in a never ending hurricane. He then comes to realize that "those who undergo this torment are damned because they sinned within the flesh, subjecting reason to the rule of lust" (Alighieri, 5. 37-39). Lust contrasts God's love because it is a sexual desire that dishonors its object and disregards God. It's the corruption of a good thing by the absence of honorable commitment and by the absence of a supreme regard for God. If your sexual desire is not guided by respect for the honor of others and regard for the holiness of God, it is lust.