There is great variability in people's tolerance of pain and their ability to describe their symptoms. Psychological factors can make things worse. The source of the problem may be remote from the location of the pain. The diagnosis of headaches may have so many variables that the task is too complex for the human mind to consider and it may be a task more suitable for a computer. Diagnostic reasoning is the process of assembling evidence to support disease identification or diagnosis.
Diagnosis is an act of inferential logic.
Diagnoses can be arrived at by many different reasoning processes. Physical diagnosis is the determination of the disease based on inspection, palpation, percussion, and auscultation. Clinical diagnosis is based on signs, symptoms and laboratory findings. Diagnosis ex juvan'tibus is based on the result of therapy. If a clinician cannot conclusively establish a diagnosis, the result of conservative trial therapy to deal with the problem is an important diagnostic tool.