These have been "arranged by the wisest men of all time, under four general heads," and are defined by Ruskin as "Prudence or Discretion (the spirit which discerns and adopts rightly), Justice (the spirit which rules and divides rightly), Fortitude (the spirit that persists and endures rightly), and Temperance (the spirit which stops and refuses rightly). These cardinal and sentinel virtues," he adds, "are not only the means of protecting and prolonging life itself, but are the chief guards or sources of the material means of life, and the governing powers and princes of economy."