One of the fascinating aspects of this novel is the way that flashbacks are used extensively in order to highlight the impact of the past on the present and to establish the continuing relevance that the past has on what is going on in the present. The structure serves to emphasise the novel's message of determinism, which explores the way in which there is no such thing as free will, as choices that are apparently made freely are shown to be made only in the light of what has gone before. The past thus is shown to control the present. This is most evident in the character of Joe, who although he is apparently presented as a free adult in charge of his own destiny, is unable to break free from his past experiences, in particular his time in the orphanage and his period spent with the McEacherns. Note how this theme of the past controlling the present is identified in the following quote:
A man will talk about how he’d like to escape from living folks. but it’s the dead folks that do him the damage. It’s the dead ones that lay quiet in one place and don’t try to hold him, that he can't escape from.
Determinism is thus explored in the way that past events and past characters, even those who are dead, are shown to be more powerful than present events and people. The plot construction of this novel questions the extent to which past events can actually be considered to be in the past.
Light in August, a novel about hopeful perseverance in the face of mortality, features some of Faulkner’s most memorable characters: guileless, dauntless Lena Grove, in search of the father of her unborn child; Reverend Gail Hightower, who is plagued by visions of Confederate horsemen; and Joe Christmas, a desperate, enigmatic drifter consumed by his mixed ancestry.