To be convicted of a crime in the United States, a person must be proven guilty 'beyond a reasonable doubt'. But what is reasonable doubt? Even sophisticated legal experts find this fundamental doctrine difficult to explain. In this accessible book, James Whitman digs deep into the history of the law and discovers that we have lost sight of the original purpose of reasonable doubt. It was not originally a legal rule at all, he shows, but a theological one. The rule as we understand it today is intended to protect the accused. But Whitman traces its history back through centuries of Christian theology and common-law history to reveal that the original concern was to protect the souls of jurors. In Christian tradition, a person who experienced doubt yet convicted an innocent defendant was himself guilty of a mortal sin. Jurors fearful for their own souls were reassured that they were safe, as long as their doubts were not 'reasonable'. Today, the old rule of reasonable doubt survives, but it has been turned to different purposes. The result is confusion for jurors, and a serious moral challenge for our system of justice.

詹姆士·Q.惠特曼，耶象大学法学院比较法和外国法的福特基金教授。精通德语、法语、拉丁语，掌握意大利语，可以阅读、听说西班牙语、荷兰语，阅读古希腊文献，拥有一定的梵文、希伯来经和中文知识。研究领域包括比较法、合同法、刑事法以及欧洲法律史；出版的学术专著除了荣获美国律师协会2009年度银槌奖的《合理怀疑的起源》之外，还包括：《战争裁决：胜利法则与现代战争的形塑》（2012）；《残酷司法：刑事惩罚与美国与欧洲之间的割裂》（2003），该书2004年荣获美国犯罪学协会颁发的国际犯罪学名著奖；《日耳曼罗曼蒂克时代的罗马法遗产：历史视角和法律变化》（1990）。在国际著名学术期刊上以德语、法语以及母语英语发表学术论文39篇、书评和随笔18篇。

侣化强，湘潭大学法学院副教授，2007年8月至2008年8月公派留学美国福德汉姆大学（ FordhamUniversity）法学院。

李伟，中央财经大学法学院讲师，德国马普外国与国际刑事法律研究所访问学者（2006年）。