Abstract

Subjective probabilities play a significant role in the assessment of evidence: in other words, our background knowledge, or pre-trial beliefs, cannot be set aside when new evidence is being evaluated. Focusing on homeopathy, this paper investigates the nature of pre-trial beliefs in clinical trials. It asks whether pre-trial beliefs of the sort normally held only by those who are sympathetic to homeopathy can legitimately be disregarded in those trials. The paper addresses several surprisingly unsuccessful attempts to provide a satisfactory justification for ignoring the pre-trial beliefs of the homeopathic community. The ensuing diagnosis of the difficulties here emphasizes that the reason the arguments for choosing the pre-trial beliefs of the conventional community seem insufficient is not the arguments per se. It is rather that there is no cogent argument for choosing the conventional stance which would at the same time rationally persuade a member of the homeopathic community. The paper concludes that, once we understand that this is the predicament, there is no genuine reason to doubt the reasoning that leads us to reject the pre-trial beliefs of the homeopathic community.