Apostles of Certainty: Data Journalism and the Politics of Doubt traces the way American journalists have made use of quantitative information in their news reporting from the early twentieth century to the present day. In so doing, it examines changing notions of journalistic objectivity and truth telling, particularly as these have evolved alongside social science disciplines such as political science and sociology. Apostles of Certainty uses methodological techniques pioneered in science and technology studies to link the study of newsroom ontologies and epistemologies to a broader analysis of how public knowledge is produced and distributed in the digital age. Though largely historical, the book also sheds light on politics and media in the twenty-first century, with findings that speak to current public conversations around so-called post-truth and the spread of fake news. The book concludes that, viewed over the long term, journalistic reporting in the United States has improved in its accuracy, subtlety, and professional self-certainty, but we have not witnessed a simultaneous improvement in the conduct of US political discourse. In part this is because political journalism only influences politics to a limited degree. To the degree it does have an impact on the political process, the book argues that data-oriented journalism plays a largely tribal and aesthetic role and divides Americans into empirical “tribes” based in part on the perceived elitism of data-based reporting.