Indeed, Greene suggests that the answers may not really matter. ‘Innocence,’ he writes, ‘is a kind of insanity.’ When it comes to the exercise of power, the idealist intent on doing God’s work is likely to wreak as much havoc as the cynic who rejects God’s very existence. Those who credit themselves with acting at the behest of the purest motives are hardly less likely to perpetrate evil than those who dismiss ideals as sheer poppycock. Only those who recognize the omnipresence of sin—recognizing first of all that they themselves number among the sinful—can possibly anticipate the moral snares inherent in the exercise of power. Righteousness induces blindness. The acknowledgment of guilt enables the blind to see. To press the point further, the statesman who assumes that ‘we’ are good while ‘they’ are evil—think George W. Bush in the wake of 9/11—will almost necessarily misinterpret the problem at hand and underestimate the complexity and costs entailed in trying to solve it. In this sense, an awareness of one’s own failings and foibles not only contributes to moral clarity but can help guard against strategic folly.
Andrew Bacevich’s summary of Graham Greene’s view.