The author doesn’t conclude that “any attempt at explanation does violence to the unity” of something. Rather, the author suggests that differing conceptions of fiction can explain why Jewett’s work lacks certain things contained in the work of domestic novelists.

The author doesn’t suggest that there are any incompatible explanations for the lack of child-rearing and religious content in Jewett’s work. The author never indicates that these explanations can’t both play a role in Jewett’s work.

The author never suggests that different explanations are actually similar. Rather, the author suggests that differing conceptions of fiction can explain why Jewett’s work lacks certain things contained in the work of domestic novelists.

The author doesn’t make a counterargument against the need for a hypothesis to explain the absence of child-rearing and religion in Jewett’s work. Rather, the author proposes a hypothesis that differing conceptions of fiction as an explanation for the lack of those things in Jewett’s work.

The author begins by mentioning explanatory hypotheses — the migration of the rural young to cities or the increasing secularization of society. The author comments favorably on these — “such factors may help to explain the differences.” But the author advocates for another explanation — the differences “ultimately reflect different conceptions of the nature and purpose of fiction.”