Butler’s imaginative creation of a near-future scenario in which a heritable condition is created by the cure for cancer introduces a scientific conflict that is somewhat plausible. However, Butler is ultimately far less interested in the hard details of how an illness like Duryea-Gode Disease (DGD) could come about than she is in using it to explore what it means to be human. To that extent, “The Evening and the Morning and the Night” is a very human story in that the central characters are coming to terms with their mortality and their moral responsibility to those around them.

The theme of Illness, Marginalization, and Institutionalization is central to the motivations of the characters in the story. The main characters frame their experiences and their worldviews through their status as DGDs, including the social stigma and the seemingly inevitable short and miserable lives that will result from the condition. Though both Alan and Lynn seem to be outwardly ambitious and hardworking, they feel that they are merely distracting themselves from their fate, “marking time” in order to distract from the “terror” of their condition (37). They don’t initially have an alternative explanation for their high achievement and hard work other than to think of it as something they don’t fully understand about themselves, a reaction to the deep despondency they feel.