How Adam could perform sin if the creation was good? How he could be free?
First, please understand that I am only trying to explain Augustine’s argument and not maintaining that it is necessarily correct.
As I understand it, Augustine is saying that while Creation is good, Adam was originally free to misuse the good in ways that are evil, or would have an evil outcome, through the choice of his own free will. This, Augustine argues, resulted in Adam’s sin. It was not pre-determined, however. Adam had free will and it enabled him to make both good and bad choices, and he chose to misuse it. Adam, as the “prototype” man, thereby corrupted free will. This was the fall.
It was Original Sin, and it became the natural state of all men who would follow Adam. Absent the power of grace, man, in his corrupted state, could only make bad choices, or more correctly, could only choose vice. It does not mean he necessarily would make them but that when it came to a choice he would err as a result of his corrupted nature and free will. Man had lost the power of moral discernment. This was punitive and imposed by God as a result of Adam’s sin. This does concern sins of the flesh generally, but the concept is wider.
Why does it follow that Adam, and his descendants in their natural condition, could only chose vice? I think what Augustine is saying is that these bad choices are not made by free will at all. Man, as punishment for Adam’s sin, lost that original capacity. His very nature was corrupted, and hence it would follow he was only free to err. It is the necessary result of any choice since to err is his very nature, and he cannot do otherwise. But Original Sin is absolved by baptism, and free will is thereby restored through the power of grace.
Nevertheless, true free will was lost. Man by his nature remains weak and is given to sin, and he is only able to chose the good through the power of grace. This is how I understand
Augustine’s argument. Augustine views the nature of man as fundamentally flawed, and the weakness is primarily that of the flesh. Absent moral discernment, concupisence, as Augustine often terms it, compels man to err absent the power of grace. This weakness of the flesh is called “fomes peccati” in Catholic theology, which is the selfish human desire for an object, person or experience. In Augustine’s view, as in Catholic theology, it is an innate tendency in human beings. The flesh is weak and prone to do what is proscribed.