Blood and belief is an ambitious book. Its strengths are, first, that it asks the right question and, second, that it adopts what is, in my judgement, both the currently popular and the fundamentally appropriate method of approaching that question. Biale asks why blood symbols and blood practices became so central to Christians and Jews, particularly in the later Middle Ages and again in the twentieth century. Despite claims on the book's jacket that he treats ‘the divide between Judaism and Christianity’, his actual argument, paralleling the work of contemporary scholars such as Israel Yuval, is that Judaism and Christianity were neither simply opposed, strategically or theologically, nor simply borrowers of each other's ideas; rather each engaged in self-definition in the context of knowledge of and contact with the other. Biale argues that both Christians and Jews moved in the Middle Ages to make blood far more central symbolically than it had earlier been: blood as human sacrifice (of Christ or of the Jewish martyrs of the First Crusade), blood as covenant or link constituting community (through either abstention from or consumption of it), and blood as vengeance (God's and humankind's). Blood returns, he argues, in the twentieth century in Nazi propaganda and in Zionism, both with its older meanings of sacrifice and vengeance given even more virulent interpretations and with new nationalist and racialist understandings. The limitations of Biale's sweeping treatment are, first, that there is a certain confusion of levels of argument. For example, in the early part Biale maintains that, in the absence of an articulated theology of blood in the Hebrew Scriptures, blood must be seen as a kind of priestly power grab – an argument which not only confuses function with meaning but is also contradicted by his own convincing and thoughtful analysis of menstrual taboos, which gives a theological and symbolic interpretation as well as a functionalist one. Second, chapters iv and v substitute summaries of specific Nazi or Zionist works for deeper analysis of social context or European-wide trends. Third, there is a tendency (often found in postmodern analysis of symbols) to slide between actual and symbolic. It sometimes seems hardly to matter whether an account of killing or desecrating or suicide is a literary construction or an event. Yet one cannot help feeling, as a historian and a human being, that the difference matters a great deal. Fourth, and most serious, is the absence of treatment of the early modern period, during which blood – as libel, as sacrifice and as understanding of community – played a somewhat less central role in both Christian and Jewish traditions. If we are to understand its reappearance after 1840 and the ways in which the new blood of lineage, race and nation was fundamentally different from earlier ideas – in other words, if we are to answer Biale's question ‘why blood?’ historically – we need more consideration of the relatively peaceful period in blood politics that came between the late Middle Ages and the late nineteenth century.