There have been numerous publications on the advantages and disadvantages of estimating natural (pure) effects compared to controlled effects. One of the main criticisms of natural effects is that it requires an additional assumption for identifiability, namely that the exposure does not cause a confounder of the mediator-outcome relationship. However, every analysis in every study should begin with a research question expressed in ordinary language. Researchers then develop/use mathematical expressions or estimators to best answer these ordinary language questions. When a recanting witness is present, the paper illustrates that there are no violations of assumptions. Rather, using directed acyclic graphs, the typical estimators for natural effects are simply no longer answering any meaningful question. Although some might view this as semantics, the proposed approach illustrates why the more recent methods of path-specific effects and separable effects are more valid and transparent compared to previous methods for decomposition analysis.

翻译：已有大量文献讨论了估计自然（纯）效应与控制效应的优缺点。对自然效应的主要批评之一在于，其可识别性需要额外假设，即暴露变量不会引起中介-结果关系的混杂因素。然而，每项研究的每个分析都应始于用日常语言表述的研究问题。研究人员随后开发或使用数学表达式或估计量，以最佳地回答这些日常语言问题。本文表明，当存在撤销见证时，并不存在假设违反的情况。相反，使用有向无环图，自然效应的典型估计量已不再回答任何有意义的问题。尽管有人可能认为这仅是语义问题，但本文提出的方法说明了为何近期提出的路径特异性效应与可分离效应方法在分解分析中比以往方法更为有效和透明。