Joyce’s tone in “Grace” is satirical and gently mocking. In addition to actively satirizing the Catholic Church (via the transaction-oriented Father Purdon), he is also gently mocking Kernan and his group of friends for their lack of spiritual integrity. As a group, they are more interested in arguing over papal mottos and criticizing Protestantism than actually engaging with important religious questions like morality and redemption.
Though Joyce does not have his third-person narrator offer direct commentary on the men’s behavior, his teasing tone comes across in his decision to have the characters speak and behave in such unenlightened ways. Take the following passage, for example, in which Kernan almost refuses to attend the Catholic retreat because they use candles:
—All we have to do, said Mr Cunningham, is to stand up with lighted candles in our hands and renew our baptismal vows.
—O, don’t forget the candle, Tom, said Mr M’Coy, whatever you do.
—What? said Mr Kernan. Must I have a candle?
—O yes, said Mr Cunningham.
—No, damn it all,” said Mr Kernan sensibly, I draw the line there. I’ll do the job right enough. I’ll do the retreat business and confession, and ... all that business. But ... no candles! No, damn it all, I bar the candles!
Kernan shouts “damn it all” and that he “bar[s] the candles” because, as someone who was raised Protestant and only converted to Catholicism for practical matters (to marry his wife), using candles in church is unknown to him. Having Kernan react in this hyperbolic way to a small matter is Joyce’s way of poking fun at the supposedly significant differences between Catholicism and Protestantism.