The logic of diagnosis: Peirce, literary narrative, and the history of present illness.

This essay presents a theoretical construct upon which to base a working--"pragmatic"--definition of the History of Present Illness (HPI). The major thesis of this essay is that analysis of both the logic of hypothesis formation and literary narrative--especially detective stories--facilitates understanding of the diagnostic process. The essay examines three elements necessary to a successful development of a patient's HPI: the logic of hypothesis formation, based upon the work of the philosopher-logician, Charles Sanders Peirce; the organization of knowledge in relation to structures of narrative; and the feedback necessary to the successful physician-interviewer. It concludes with a systematic description of the design of hypothesis formation within diagnoses.