The word psychology first appeared in the English language in the 17th century and derives from psyche (soul) and ology (study of). As a philosophical subject, it considered the mid and body as separate entities. French philosopher Rene Descartes reasoned "the mind and body were separate because if something is taken away from the body (i.e. a foot), nothing is considered to have been lost by the mind." His philosophy, known as dualism (dual condition), determined that the mind does not exist in space as ordinary physical substances do; it can think for itself and has purpose and freedom of will.
As long as man's problems were those of the soul, it was the domain of the clergy and religion to to address those problems.
Later, in 1808 the word "psychiatry" was coined by Johann Christian Reil. This word means "doctoring the soul", coming from psyche (soul) and iatros (doctor). This new word allowed psychiatrists to take matters of the soul away from religion and into their own, incapable hands.