Edward T. Oakes in a fine article quotes Pascal:
The greatness of man is so evident that it is even proved by his wretchedness. For what in animals is called nature we call wretchedness in man; by which we recognize that, his nature now being like that of animals, he has fallen from a better nature which once was his. For who is unhappy at not being a king except a deposed king? Who is unhappy at having only one mouth? And who is not unhappy at having only one eye? Probably no one ever ventured to mourn at not having three eyes; but anyone would be inconsolable at having none.
Yes indeed, man is wretched and only man is wretched. Man's wretchedness is 'structural': man qua man is wretched. Wretched are not merely the sick, the unloved, and the destitute; all of us are wretched, even those of us who count as well off. Some of us are aware of this, our condition, the rest hide it from themselves by losing themselves in what Pascal calls divertissement, diversion. We are as if fallen from a higher state, our true and rightful state, into a lower one, and the sense of wretchedness is an indicator of our having fallen. We are in a dire state from which we need salvation but are incapable of saving ourselves by our own efforts, whether individual or collective.
Well, suppose you don't accept a word of this. And suppose you don't lapse into nihilism either. What option is left? The illusions of the Left and the notion of the perfectibility of man by his own doing? Then I recommend this passage from Reinhold Niebuhr also quoted by Oakes:
The utopian illusions and sentimental aberrations of modern liberal culture are really all derived from the basic error of negating the fact of original sin. This error . . . continually betrays modern men to equate the goodness of men with the virtue of their various schemes for social justice and international peace. When these schemes fail of realization or are realized only after tragic conflicts, modern men either turn from utopianism to disillusionment and despair, or they seek to place the onus of their failure upon some particular social group, . . . [which is why] both modern liberalism and modern Marxism are always facing the alternatives of moral futility or moral fanaticism. Liberalism in its pure form [that is, pacifism] usually succumbs to the peril of futility. It will not act against evil until it is able to find a vantage point of guiltlessness from which to operate. This means that it cannot act at all. Sometimes it imagines that this inaction is the guiltlessness for which it has been seeking. A minority of liberals and most of the Marxists solve the problem by assuming that they have found a position of guiltlessness in action. Thereby they are betrayed into the error of fanaticism.
I refuse to lapse into nihilism and I refuse to be suckered by the illusions of the Left, which illusions have been amply refuted by the horrors of the 20th century. That is why I take Original Sin seriously. But I reject Biblical literalism with its tale of a first man and a first woman in a garden. And of course I reject the idea that I am guilty because of what some other people did. So this leaves me with the task of articulating the doctrine of Original Sin/Ignorance in a way that is philosophically respectable.