“Non Sum Qualis Eram Bonae Sub Regno Cynarae” is Ernest Dowson’s most famous poem and one of the most celebrated lyrics of the legendary English 1890s. Why did it become so particularly famous? Supposing that its fame is no more than it deserves, the question might be approached from another direction: why is it so good? How persuasively can its strange success be explained? The inquiry is therefore a matter of literary history, insofar as it asks how the poem took shape, and how it found its place in the English lyrical tradition; but it is also a matter of literary criticism, in the most fundamental sense, insofar as it wants to discover and articulate, as precisely as possible, how the poem actually works to produce its very unusual and memorable effects.