The last few lines of the book give the sense that they are absolutely crucial to any interpretation of the book. Yet I've been having a rather difficult time trying to decipher them. At this point, Police Inspector Scobie (the novel's main character)has just committed suicide, and his wife is discussing the tragedy with the local priest.
"(Mrs. Scobie) He must have known that he was damning himself."
..."For goodness' sake, Mrs. Scobie, don't suppose that you - or I - know a thing about God's mercy. ... It may be an odd thing to say - when a man's as wrong as he was - but I think, from what I saw of him, that he really loved God."
"He certainly loved no one else."
"And you may be in the right of it there, too."
Did Greene intend us to take the priest's final analysis of Scobie as accurate? All things considered, I'm inclined to think that he did. It's the "last word" of the book, so to speak. The priest, though not a saint, seems to be a man of integrity and of real faith in the Church. But if one accepts this analysis, what can one make of it?
A little backstory is definitely necessary. (How, indeed, could the ending of any book be quite comprehensible outside the context of the book itself?) Scobie's driving characteristic (in the literal sense that it really provides the motive for just about every one of his actions) is an overwhelming desire that those around him be "happy". However, he believes hat he can keep others happy by keeping them content. By being perfectly kind and creating an atmosphere of peace, whether the peace is true or not. This falsity is a problem from the beginning, but the habit of killing those around him with kindness leads to a fatal conclusion when he is faced with the choice of "what's right" versus "what will make everyone else comfortable". "In human relations, kindness and lies are worth a thousand truths" he believes, and even the reply from God he seems to hear in his prayer, "[to do what I ask] one of them must suffer, but can't you trust me to see that the suffering isn't too great?" isn't enough to make him choose what's right.
It's easy to see how, for all of his compassion, Scobie's love for those in his vicinity was empty. You can't really love someone by hiding the truth. Comfort is not the greatest good which you can provide another, especially when it comes at the cost of truthful and meaningful relationships with others. Moreover, at least initially, Sobie's main concern seems to be with his own peace - domestic peace in his relationship with his wife, the mental peace of having "done his duty" to those around him.
But how could the priest possibly say that Scobie "really loved God"? Scobie was fully aware that his suicide was the one of the ultimate offences against God. However, it seems as though the "heart of the matter" - his real, though distorted, love - lies in the fact that he was willing to "hurt" God in order to put an end to the pain which he knows he will continue to cause Him. Once again, it's heresy of the grossest kind. But it is perhaps the case that by rejecting all possibility of his own comfort, his own peace in a life which he knows will be inextricably tied to God, whether through an eternal rejection or eternal acceptence of God, he has shown some hint of the love necessary for salvation. His hopeless explanation, "I can't shift my responsibility onto you. I love you, and I won't go on insulting you at your own altar" does perhaps contain just enough love to leave him open to God's mercy. God, whose "weakness", according to Greene, is precisely the enormity of His love, can turn even Scobie's assault against this into a saving grace. "Don't suppose, Mrs. Scobie, that you - or I - know a thing about God's mercy."