the irony involves
Thomas’s repeated assertion that he will not abide Sarah’s presence in the house, because in his eyes she represents immorality and dissolution. “Thomas was not cynical,” we are told, “and so far from being opposed to virtue, he saw it as the principle of order and the only thing that makes life bearable.” Sarah, whom Thomas refers to as the “little slut,” represents, in his eyes, the antithesis of virtue and order.
His mother, meanwhile, is possessed, in Thomas’s estimation, of “the best intentions,” yet is blinded by her charitable impulses; her tendency is “to make a mockery of virtue, to pursue it with such a mindless intensity that everyone involved was made a fool of and virtue itself became ridiculous.”
Thomas considers himself a model of virtue and purity, but for him, virtue must exist in moderation, because “a moderation of good produces likewise a moderation of evil,” something that Thomas feels his mother would understand “[h]ad she been in any degree intellectual.”
The irony is that while Thomas proclaims himself virtuous, his propensity to withdraw from what he sees as an excess of charity on his mother’s part renders him practically ineffectual; he is paralyzed and unable to commit to any action, good or bad:...