Boston progressive editor Benjamin O. Flower (1858-1918) pushed for a wide range of women-friendly reforms and publicized many turn-of-the-century feminists. He saw "female purity" as the engine of progress - the moral purification women inspired was the backbone of a radical regeneration of the country that would lead to individual, social, economic, political and family transformations. This article purposes to explore this social imagination of purity, its scope and its evolution. It examines Flower's role in the "Purity Movement," a crusade that aimed at putting an end to prostitution - within and without marriage - and to low age of consent laws. For Flower, male immorality, urban poverty, and ignorance about sex accounted for women's degradation. Realistic literature and journalistic exposures were therefore the necessary tools to regenerate society. This article also analyzes the ambiguous trajectory of Flower's vision of "female purity". He saw in Mary Baker Eddy, the founder of Christian Science, the embodiment and the logical outcome of his feminist struggles. However, this new movement only led to social apathy. His exhortations were also predicated upon essentialization (men as beasts or pure intellect and reforming energy, women as victims or as models of moral idealism) and the traditional postulates of Victorian culture (the centrality of home). Finally, in his last years, Flower embarked on a crusade against the "menace" Catholicism posed to women. This episode reveals the nativist potential of imagined purity as Flower tolerated nothing short of an ethereal "feminine" idealism. http://nuevomundo.revues.org/66381