How does the soul relate to the body? Through the ages many religions and intellectual movements have posed answers to this question. Many have gravitated to the notion of the subtle body, positing some kind of subtle entity that is neither soul nor body, but some mixture of the two. This book traces the history of this idea from the late Roman empire to the present day, touching on how philosophers, wizards, scholars, occultists, psychologists, and mystics have engaged with the idea over the past two thousand years.