Her statistics were more than a study, they were indeed her religion. For her Quetelet was the hero as scientist, and the presentation copy of his Physique sociale is annotated by her on every page. Florence Nightingale believed -- and in all the actions of her life acted upon that belief -- that the administrator could only be successful if he were guided by statistical knowledge. The legislator -- to say nothing of the politician -- too often failed for want of this knowledge. Nay, she went further; she held that the universe -- including human communities -- was evolving in accordance with a divine plan; that it was man's business to endeavor to understand this plan and guide his actions in sympathy with it. But to understand God's thoughts, she held we must study statistics, for these are the measure of His purpose. Thus the study of statistics was for her a religious duty.
K. Pearson The Life, Letters and Labours for Francis Galton, vol. 2, 1924.