In Dante’s philosophy, the most basic and most forgivable category of sin is incontinence, or a lack of self-control. The incontinent sinners constantly indulge their impulses. Often, they commit sins to sate their physical and materialistic urges. The core of the incontinents’ wrongdoing lies in their failure to use their God-given minds to judge their actions as good or evil. Because they do not think and act on their feelings, the incontinent sinners deny their human civility. This is why Dante often paints them in animal imagery. In the sinners’ defense, however, incontinence is instinctive and primitive; lust, hunger, and wrath are universal urges, felt by all human beings and even animals.
In Dante’s Inferno, the text suggests that the incontinent sinners behave in a more bestial fashion than a human one.
If Nature is an expression of God’s will and the incontinent sinners only follow their natural instincts, then the incontinent sinners did not really sin.