"But Proportion has a sister, less smiling, more formidable, ..." — Virginia Woolf quote meaning

But Proportion has a sister, less smiling, more formidable, a Goddess even now engaged--in the heat and sands of India, the mud and swamp of Africa, the purlieus of London, wherever in short the climate or the devil tempts men to fall from the true belief which is her own--is even now engaged in dashing down shrines, smashing idols, and setting up in their place her own stern countenance. Conversion is her name and she feasts on the wills of the weakly, loving to impress, to impose, adoring her own features stamped on the face of the populace. At Hyde Park Corner on a tub she stands preaching; shrouds herself in white and walks penitentially disguised as brotherly love through factories and parliaments; offers help, but desires power; smites out of her way roughly the dissentient, or dissatisfied; bestows her blessing on those who, looking upward, catch submissively from her eyes the light of their own. [She] had her dwelling in [his] heart, though concealed, as she mostly is, under some plausible disguise; some venerable name; love, duty, self sacrifice. How he would work--how toil to raise funds, propagate reforms, initiate institutions! But conversion, fastidious Goddess, loves blood better than brick, and feasts most subtly on the human will.