While the violence in Flannery O'Connor's novel is largely associated with fire, the intractable and fatalistically depicted family "inheritance" that drives the novel is repeatedly tied to blood. 

The old man describes Rayburn, the schoolteacher, in his connection to the Tarwater family by referring to the idea that:

"'Good blood flows in his veins,' the old man said. 'And good blood knows the Lord and there ain't a thing he can do about having it. There ain't a way in the world he can get rid of it'" (Part One: II).

Blood becomes a motif that suggests two things: genealogical connection and the burden of prophecy. 

Prophecy functions almost as a curse in both old Tarwater and young Tarwater. More references to blood solidify the notion that this mandate to profess and to baptize works as a kind of fate for the boy that is instilled by blood and awakened by the older Tarwater's constant exhorations. 

"[...] the old man's words had been dripping one by one into him and now, silent, hidden in his bloodstream, were moving secretly toward some goal of their own" (Part One: II).

The old man is similarly bound to prophecy by blood, it would seem, just as he is bound to his family. When confronted by Rayburn, the old man feels that "[h]is prophet's blood surged in him, surged to floodtide for a miraculous release" (Part One: II). Thus blood is associated with an inner vitality or energy that seems to come from God and which almost always takes a violent manifestation. 

Throughout the novel the family is at odds with itself. The individuals that make up the family are also engaged in an interior turmoil, struggling against themselves or against some part of their sense of fate, sense of duty and sense of reality. 

Even Rayburn is affected by the sense that his blood connects him to a fatalistic, violent and irrepressible urge. Rayburn's reflections on his life with Bishop, the disabled child, sometimes leave him "trembling for his sanity" and he explains this to himself with the idea that

"It was only a touch of the curse that lay in his blood" (Part One: IV). 

Later, young Tarwater thinks about how the "Lord out of dust had [...] made him blood and nerve and mind, had made him to bleed and weep and think" (Part Two: III) and this thought is directly connected to the boy's sense of his fate, which is a mandate to baptize Bishop. This urgency in young Tarwater is what eventually leads him to kill Bishop and thus to enact the self-destructive aspect of the violence in his "blood." 

"In the end, Tarwater succumbs to his religious calling, and it is less a victory than a capitulation when he embraces his role as a prophet of God" (eNotes).

The notion of identity and heredity are closely linked in The Violent Bear It Away in terms of the idea of essential struggle. Each of the main characters can be said to engage in the same struggle - to act upon the urges of the blood, which old Tarwater suggests is linked to a knowledge of God, or to deny that urge in the blood. 

Given this connection between the characters, drawn by blood, as it were, the blood imagery comes to represent man's spiritual conflict in the modern world. Having inherited either (culturally or spiritually) an opportunity for faith and submission to God, the Tarwaters have also been faced with opportunities to join a secular world that is less violently, less extremely bound to the rigid dictates of prophecy and prophetic vision. 

O'Connor's characters are sometimes difficult to interpret without irony in a modern context because, in part, the morality of faith tends to be set against a secular morality and the morality of faith is often the more accepting of violence and violent action. The blood that leads Tarwater to baptize also leads him to kill.