The narrator's tone remains fairly detached throughout East of Eden, critiquing and interpreting the characters' actions as allegories. In certain passages, Steinbeck narrates how one might expect God to do, which is tonally appropriate for an allegorical reinterpretation of Genesis.
The narrator in East of Eden generates a critical tone throughout the novel, calling various hypocrisies and moral inconsistencies to readers' attention. In large part through his narratorial contributions, Steinbeck explores moral relativism by retelling and recontextualizing biblical stories.
Chapter 3 provides a prime example of such subtle tonal contributions that critique religion and tease out moral relativism:
Not from things said but from the tone in which other things were said, [Adam] knew that he had once had a mother and that she had done some shameful thing, such as forgetting the chickens or missing the target on the range in the woodlot.
In this excerpt, the narrator's tone takes on the same quality of Adam's as a young child. Being young, Adam has not yet learned to associate sex and nakedness with shame and immorality. Thus, the narrator understates shame both as a means of showing Adam's age and of establishing a tone critical of religion (and how it teaches adults to fear sexual transgression).