In several recent posts, I argued that when a person is to some degree determined toward evil on account of an external cause, he is to that degree less free and responsible for doing the evil. In a similar vein someone might argue: it is practically speaking a foregone conclusions that we are going to commit many sins, because we are born sinners, and we are born sinners not because of anything we did (as in Origen's account), but because of Adam. It's his fault, not ours. He's really the one responsible for our sins!
There are a couple of complementary ways to approach this objection. First, we may insist, as the Early Church Fathers, as well as nearly all the Eastern Fathers tend to do, that we still retain the basic freedom to choose what is good; the divine spark and light of the Spirit in the soul has been dimmed, but not totally extinguished from the soul. This is the objective approach to answering the objection.
But how do we reconcile all these affirmations, that (1) to the degree that one person's bad action is predictable on account of the agency of another person, the former is less free and less responsible for that bad action, that (2) on account of Adam's sin, we are virtually certain to commit numerous sins, and that (3) we remain free and responsible for our sins?
The first way of doing so is to recognize that our present freedom, while real freedom, is merely a dim shadow of the freedom that is possible to the human spirit. The freedom of all of our free acts and choices, both good and evil, is a shadow of the freedom of a man whose spirit possesses true mastery of choice, for whom the "perishable body" does not weigh down the soul. If our sins are ten thousand times less voluntary than Adam's sin (which may or may not be true), this does not mean that our sins are involuntary, or that we are not free, but that Adam's freedom was a freedom greater than we can possibly imagine.
The other way to answer the objection is that whatever the cause of our sinfulness, that is, our separation from the holiness of God and our tendency to sin, the fact remains that it is we who are sinful, we who sin, we who so often act in disgraceful and shameful fashions. C.S. Lewis illustrates this well in the Problem of Pain:
Theoretically, I suppose, we might say 'Yes: we behave like vermin, but then that is because we are vermin. And that, at any rate, is not our fault.' But the fact that we are vermin, so far from being felt as an excuse, is a greater shame and grief to us than any of the particular acts which it leads us to commit. The situation is not nearly so hard to understand as some people make out. It arises among human beings whenever a very badly brought up boy is introduced into a decent family. They rightly remind themselves that it is 'not his own fault' that he is a bully, a coward, a tale-bearer and a liar. But none the less, however it came there, his present character is detestable. They not only hate it, but ought to hate it. They cannot love him for what he is, they can only try to turn him into what he is not. In the meantime, though the boy is most unfortunate in having been so brought up, you cannot quite call his character a 'misfortune' as if he were one thing and his character another. It is he—he himself—who bullies and sneaks and likes doing it. And if he begins to mend he will inevitably feel shame and guilt at what he is just beginning to cease to be.
Augustine emphasizes (in some respects excessively) this second approach to the state of sinfulness in which we are born. This approach, in contrast to the first, is principally subjective, focusing on our experience of a separation from God, our corresponding behavior, and consequent shame. Though this second approach would not suffice on its own to answer the objection that would deny our responsibility for sin, it is a valuable complement to the first approach.