"Amor Mundis" is a poem about moral discretion. Rossetti flirts with the concepts of right and wrong. In a conversation between two lovers on a walk, she alludes to the moral dilemma of difficulty. Generally the difficult things to do are the ones worth doing, but that's what makes doing good such a challenge for people. The two lovers in this poem take opposite stances about which direction to walk. He wants to continue uphill because he believes the downhill path leads to hell. She, however, is just tired and wants to walk downhill for a change. They part ways.
In the course of the argument, readers can see the entire moral dilemma laid out plainly. She wants to take the easier path because she's exhausted from walking uphill all this time, but she's told that it's wrong to do so. He exerts his moral virtue to resist the temptation to follow her down the hill. In the end, then, Rossetti tells us that morality is subjective. The woman chose to walk downhill because she felt that she was justified in doing so because she was tired, but he wouldn't follow because his conviction was too strong to allow him to do that.
