How we cite our quotes:
And, truth to tell, nothing was more important on earth than a child's suffering, the horror it inspires in us, and the reasons we must find to account for it. (4.4.9)
Father Paneloux is trying to justify the senseless suffering of Jacques Othon by using religion; the way that the narration presents this argument is mocking to say the least.
Thus he might easily have assured them that the child’s sufferings would be compensated for by an eternity of bliss awaiting him. But how could he give that assurance when, to tell the truth, he knew nothing about it? […] No, he, Father Paneloux […] would stand fast, his back to the wall, and face honestly the terrible problem of a child’s agony […].
It crossed Rieux’s mind that Father Paneloux was dallying with heresy in speaking thus. (4.4.9-10)
The heresy to which Rieux refers is Paneloux’s refusal to blindly justify the boy’s suffering and death. While he does go on to adamantly defend Christianity, Paneloux is definitely toeing the line here; and it does get him into the trouble with the Church, as we’ll soon see.
True, the agony of a child was humiliating to the heart and to the mind. But that was why we had to come to terms with it. And that, too, was why—and here Paneloux assured those present that it was not easy to say what he was about to say—since it was God’s will, we, too, should will it. Thus and thus only the Christian could face the problem squarely and, scorning subterfuge, pierce to the heart of the supreme issue, the essential choice. And his choice would be to believe everything, so as not to be forced into denying everything. (4.4.12)
Father Paneloux seems to be defending his religion simply because his "back is to the wall." It seems as though he’s been cornered into believing in God, rather than volunteering to do so. This goes against the existentialism notion of radical freedom – that everything, everything is a choice.