The relation between experience and knowledge has been the subject of several debates in the sociology of knowledge, especially with regard to medical knowledge. The disease is experienced by the patient and the physician, who has the knowledge of disease, conducts the diagnoses and provides treatment. This poses two questions: Does the patient, who experiences the disease, have knowledge? Does the physician, who knows the disease and its cure, have recourse to experience? How does epistemology address the relation between the ontology of the patient the layman and the doctor the specialist? After a presentation of the problematic as it reveals itself in the analysis of biomedicine, the paper proceeds, based on fieldwork with siddha practitioners in Tamil Nadu, to examine the siddha medicine approach to these issues.