 In medieval Islamic medicine in particular, the study of mental illness was a speciality of its own, and was variously known as "al-‘ilaj al-nafs" (approximately "curing/treatment of the ideas/soul/vegetative mind), "al-tibb al-ruhani" ("the healing of the spirit," or "spiritual health") and "tibb al-qalb" ("healing of the heart/self," or "mental medicine").The Classical Arabic term for the mentally ill was "majnoon" which is derived from the term "Jenna", which means "covered".It was originally thought that mentally ill individuals could not differentiate between the real and the unreal.