This explains the apparent contradiction of crusading throughout the later middle ages; its ineffectiveness failed to destroy sustained communal commitment to the idea or understanding of its ideology and ideals. This was not caused by some sort of collective escapism or mental atrophy. Rather, the crusade mentality, transmitted through long habit, current liturgy and constant renewal in fresh appeals for alms, tax, purchase of indulgences and, occasionally, armed service, framed a way of regarding the world. This mentality, widely dispersed through society, allowed the expression of faith and identity through social rituals and religious institutions without the necessity of individual political or military action. The relative scarcity of crucesignati was masked by cultural ubiquity. Independent of fighting and wars, crusading evolved as a state of mind; a means of grace; a metaphor and mechanism for redemption; a test of human frailty, Divine Judgment and the corruption of society. Crusading became something to be believed in rather than something to do.
—Christopher Tyerman, God’s War: A New History of the Crusades, pp. 825—-26