Toward the end of "The Boarding House," Mr. Doran contemplates the consequences he might face should people in his community find out about his extramarital affair with Polly. Such accusations might very well ruin the career he spent years building up through "industry and diligence." He ruminates on the path he took from that of a carefree, reckless youth to a responsible and industrious adulthood, using idiom to express this change:
As a young man he had sown his wild oats, of course; he had boasted of his free-thinking and denied the existence of God to his companions in public-houses.
The idiom "to sow one's wild oats" comes from old English farming wisdom regarding the planting of oat crops. According to this commonly-held wisdom, if one sowed wild oats as opposed to the better, more cultivated variants, the crop produced might not be as plentiful. The idiom therefore refers to impulsive, risky actions taken that one may come to regret later.
Mr. Doran uses the idiom to imply that his youthful "free thinking" and brash declarations of atheism were behaviors he grew to regret in adulthood, once given the opportunity to replace those behaviors with more pious and conformist tendencies. This assertion is one that Joyce likely does not intend readers to take at face value, given his propensity for critiquing the Catholic Church and its moral vice grip on Irish society. Rather, Joyce introduces this idiom and the discourse surrounding it as a means of emphasizing Mr. Doran's religious guilt and compensatory attempts at conformism.
