The fortune that Cathy leaves to Aron, the third such inheritance in the novel, is a symbol of the sin that has run through the Trask family ever since Cyrus’s original dishonesty and embezzlement. Cyrus leaves his tainted inheritance to Charles and Adam, and then Charles leaves an inheritance to Adam and Cathy. As a result, Cyrus’s fortune forms the core of Charles’s, and Charles’s then forms the core of Cathy’s. This family money represents an extraordinary legacy of dishonesty and evil passed down through the generations—Cyrus’s was likely earned through theft, and Cathy’s was earned through theft, extortion, and prostitution. The inheritance thus becomes a symbol of the idea that the sin of one generation is passed onto the next—the idea of original sin that came about when Adam and Eve were expelled from Eden. In this light, Adam, in a way, proves his essential goodness by squandering his own fortune; Cyrus, Charles, and Cathy, on the other hand, come across as evil by virtue of the fact that they increase their own fortunes. This idea of inherited sin is what makes Aron unable to stand the sight of his mother as a prostitute. Aron believes, as Cal has throughout the novel, that Cathy’s wickedness taints him morally and inevitably dooms him to evil.
In every prior instance of an inheritance in East of Eden, the money is divided evenly between two people, diffusing the legacy of sin that the money represents. In the case of Cathy’s fortune, however, Aron is the sole inheritor. Because Aron so fully accepts the idea of hereditary sin when the sight of Cathy crushes him, it is appropriate that the symbolic legacy of sin—the inheritance—should fall squarely upon his shoulders and his alone. Cal, on the other hand, receives no part of his mother’s legacy and thus is symbolically free from the tainted inheritance that has been passed down through the Trask generations.