 Single cases are seen by some as problematic as a form of evidence particularly in the era of EBM, because they often focus on highly unusual manifestations of illness and disease, rather than typical or repeatedly observed conditions that might support generalizable rules. This feature has led some to describe medicine as a “science of particulars” (Gorovitz and MacIntyre 1976), or as an art rather than a science (Pellegrino 1979), particularly in processes of diagnosis (see  Section 9).  However standard accounts of EBM include the case series as a type of evidence, which involves the aggregation of individual cases of patients with similar attributes (e.g., who received the same treatment or therapy) who are tracked over time using descriptive data and without utilizing particular hypotheses to look for evidence of cause and effect. EBM does place the case series quite low in its hierarchy of evidence but nonetheless it is acknowledged that cases have potential usefulness especially where forms of evidence that rate more highly are not available, as may often be the case where human patients are concerned due to practical or ethical reasons, or where the available evidence at higher levels has been produced in a manner that is methodologically or otherwise flawed.