Final answer:
Augustine believes the primary sin to avoid is not using free will to choose good over sinfulness, illustrated by the willful disobedience of Adam and Eve. While original sin impacts us, Augustine advocates that we can still choose the good through our will, aided by divine grace.
Step-by-step explanation:
The primary sin of the mind one must avoid, according to Augustine, is the failure to use our free will to choose the good, being led instead towards sinfulness. He presents the conflict between two wills within a person: one that pursues goodness and the other sinful desires. Augustine argues that although we are tainted by the original sin of Adam and Eve, we possess the capacity to make moral choices, with divine grace being essential to ultimately resolving this conflict and steering us towards good.
Augustine uses the fall from grace in the Garden of Eden as an example. In the Christian and Jewish Bible narrative, Adam and Eve's disobedience led to humankind's original sin. Yet, Augustine maintains our ability to choose the good, despite this inherent sinfulness, by exercising our free will - a gift from God distinct from God's providential plan. The Manichean heresy is often cited as a contrast, where Augustine defends theological orthodoxy and the potential for human salvation through grace, rather than seeing the universe as a static battlefield of equal forces of good and evil.