Fourteenth century Europe saw a growing interest in quantification. This interest has been well studied by historians of physical sciences, but medieval scholars were also interested in the quantification of psychological qualities. In general, the quantification issues addressed by medieval scholars were theoretical, even (by our standards) mathematical, rather than those of practical measurement. There was recognition that the seriousness of a sin and the penance laid down for it should be proportionate. A number of late medieval scholars were interested in the quantification of caritas, a Latin word that is translatable as charity or loving benevolence. The scholastic interest linked to the practical issue of how caritas might become habitual through the repeated performance of virtuous acts. Gregory of Rimini’s treatment of caritas in his commentary on Peter Lombard’s Sentences illustrates how one medieval scholar related the quantification of virtue to the quantification of physical qualities such as temperature and luminescence.