This chapter examines the most controversial area where consensus is involved—establishing scientific truths. It reviews the range of positions taken by philosophers, historians and sociologists of science, from those who take a strongly positive position through to those who are largely negative about the role of consensus in establishing truth. Despite the varying views, there is some agreement from these writers about the conditions under which consensus is more likely to indicate truth: (1) The consensus needs to be rational, empirical and critically examined. (2) The group coming to the consensus needs to be diverse. (3) The group needs to be open-minded, and there is no coercion of dissenters. (4) The group needs to be sufficiently large to get reliable results. It concludes that consensus can be a strong indicator of truth under certain conditions.