Perez Zagorin writes that, "According to some philosophers, tolerance is a moral virtue; if this is the case, it would follow that intolerance is a vice. But virtue and vice are qualities solely of individuals, and intolerance and persecution the Christian Middle Ages were social and collective phenomena sanctioned by society and hardly questioned by anyone. Religious intolerance and persecution, therefore, were not seen as vices, but as necessary and salutary for the preservation of religious truth and orthodoxy and all that was seen to depend upon them." This view of persecution is not limited to the Middle Ages. As Christian R. Raschle and Jitse H. F. Dijkstra, say: "Religious violence is a complex phenomenon that exists in all places and times."