If the misery of the poor be caused not by the laws of nature, but by our institutions, great is our sin.

The sentence contrasts suffering that might be unavoidable (“laws of nature”) with suffering produced by human choices (“our institutions”). Read this way, it is a moral indictment of social arrangements—laws, economic systems, and political structures—that generate or perpetuate poverty. The force of “great is our sin” frames inequality not as mere misfortune or individual failure but as collective ethical responsibility: if poverty is socially manufactured, society is culpable and obligated to reform. The phrasing also implicitly rejects complacent appeals to inevitability (including misuses of “natural law”) to excuse injustice.