Final answer:
The author likely included Adam's confusion about Cain to create ambiguity, utilize fragmented narration, and to invite readers to reflect on complex human emotions and morality through the biblical allusion of Cain and Abel.
Step-by-step explanation:
The author's likely purpose for including Adam's confusion about who Cain is in extracts from Adam's diary is to create ambiguity and engage readers with fragmented narration. The confusion serves to highlight the complexities of human nature and morality, drawing parallels with the biblical narrative of Cain and Abel's sacrifice. It prompts readers to consider the arbitrary nature of God's favor in the biblical story and allows for reflection on themes such as jealousy, sibling rivalry, and the consequences of actions. By embedding elements of the biblical allusion within the narrative, the author connects readers to these deeper conceptual layers.