Varieties of clinical reasoning

Rationale, aims and objectives Clinical reasoning comprises a variety of different modes of inference. The modes that are practiced will be influenced by the sociological characteristics of the clinical settings and the tasks to be performed by the clinician. Methods This article presents C.S. P eirce's typology of modes of inference: deduction, induction and abduction. It describes their differences and their roles as stages in scientific argument. The article applies the typology to reasoning in clinical settings. Results The article describes their differences, and their roles as stages in scientific argument. It then applies the typology to reasoning in typical clinical settings. Conclusions Abduction is less commonly taught or discussed than induction and deduction. However, it is a common mode of inference in clinical settings, especially when the clinician must try to make sense of a surprising phenomenon. Whether abduction is followed up with deductive and inductive verification is strongly influenced by situational constraints and the cognitive and psychological stamina of the clinician. Recognizing the inevitability of abduction in clinical practice and its value to discovery is important to an accurate understanding of clinical reasoning.