Discovering what is wrong with a particular situation is one of the central activities in real life; this process is usually called Diagnosis or Diagnostic Problem Solving. The process may be viewed as the selective gathering and interpretation of information as evidence for or against the presence or absence of one or more defects in a system. This informal definition reveals that the following aspects are of central importance to diagnostic problem solving. Firstly, the gathering of information, and secondly, the interpretation of the gathered information for determining what is wrong. In medicine, the information gathering process is usually carried out in a systematic, structured fashion; because there are enormous numbers of diagnostic tests available for the clinician that cannot all be carried out. Furthermore, some diagnostic tests cause patient to suffer considerable discomfort, or carry even some risk of causing disease or death.

Although the information gathering process is a characteristic feature of diagnosis, the interpretation of information as evidence for or against a diagnostic solution is a more fundamental aspect of diagnostic problem solving. The information gathering process together with related aspects, such as the process of generating, and accepting or rejecting diagnostic hypotheses are sometimes referred to the dynamic aspects of diagnostic problem solving. In general, diagnostic problem solving, like many other forms of problem solving, may be described using the scientific notion of the empirical cycle, which describes the framework underlying empirical research. It states that empirical research encompasses: (1) formulating a hypothesis, (2) testing the hypothesis, and (3) rejecting the hypothesis when it fails to pass the tests, or accepting the hypothesis when it successfully passes the tests. The process may start again with (1), in which case the formulation of a new hypothesis possibly involves adjusting a hypothesis previously rejected. In the figure, this view of diagnostic problem solving as an instance of the empirical cycle is depicted.