This short commentary corrects an erroneous understanding of probabilistic causation in the loss-of-chance doctrine and the damage calculation method adopted in Matsuyama v. Birnbaum. The Supreme Judicial Court of Massachusetts is not alone. Many other common law courts have made the same error, including Indiana, Nevada, New Mexico, Ohio, and Oklahoma. The consistency in the mistake suggests that the error is the majority rule of damages. I demonstrate here that this majority rule is based on erroneous mathematical reasoning and the fallacy of probabilistic logic.