Clinical decision making can be described as answering one question: "What is the best next thing for this patient at this time?" In addition to incorporating clinical information, research evidence, and patient preferences, the process requires considering contextual factors that are unique to each patient and relevant to their care. The failure to do so, thereby compromising that care, can be called a "contextual error." Although proponents of evidence-based clinical decision making and many scholars of the medical interview emphasize the importance of individualizing care, no operational definition is provided for the concept, nor is any methodology proposed for the interpretation of clinically relevant patient-specific variables. By conceptualizing the physician-patient encounter as a participant-observer case study with an N of 1, this essay describes how existing approaches to studying social systems can provide clinicians with a systematic approach to individualizing their clinical decision making.