本文針對醫師臨床上進行診斷推理(diagnostic reasoning)時，在相關診斷假設(diagnostic hypotheses) 的產生(generation)與鑑別(differentiae)上，進行邏輯的觀察與探討。文章透過對「回溯推論」(abductive reasoning)與「鑑別診斷」(differential diagnosis)的討論指出：建立在語意限定詞(semantic qualifiers)、邏輯 推論技巧以至臨床決策判斷等基礎上之鑑別診斷固然為診斷推理中的重要操作；然而，診斷假設本身的 正確性與特異性才是最終引領正確診斷推論、產生病人最佳未來的必要條件，也因此必須置於醫學教育 的首要與核心的項目。

This paper focuses on physician’s clinical diagnostic reasoning process from the logical point of view. The author elucidates the relationships between two logical cores in diagnostic reasoning, “hypotheses generation” and “hypotheses differentiae” (or differential diagnosis). Through examination of the relationships between “abductive reasoning” and “differential diagnosis”, this paper illuminates that the collaboration between semantic qualifiers, logical reasoning skills and decision-making strategies are critical process in regards to differential diagnosis. However, the accuracy of hypotheses generation from clinician’s knowledge and experience as well as the extent of medical education are the key steps and thus should be put into primary consideration and acknowledge their priorities.