Humble birth did not retard his genius, nor high place corrupt his soul.

The sentence contrasts two common moral tests of character: adversity and success. “Humble birth” stands for limited social standing and opportunity; Gilbert asserts that genuine genius can emerge despite such constraints. The second clause reverses the test: attaining “high place” (rank, office, prestige) often tempts vanity or ethical compromise, yet the subject’s “soul” remains uncorrupted. Together, the line functions as a compact epitaph-like commendation, praising both innate talent and steadfast integrity across changing circumstances. It implies a belief that true greatness is measured not only by achievement but by the ability to remain morally constant when one’s social position dramatically improves.