Plotinus' mysticism of henosis, <I>unification with the One</I>, is a highly controversial topic in Plotinian scholarship. This book presents a careful reading of the Enneads and suggests that Plotinus' mysticism be understood as mystical teaching that offers practical guidance concerning henosis. It is further argued that a rational interpretation thereof should be based on Plotinus' metaphysics, according to which the One transcends all beings but is immanent in them. The main thesis of this book is that Plotinus' mystical teaching does not help man attain henosis on his own, but serves to remind man that he fails to attain henosis because it already pertains to his original condition. Plotinus' mysticism seeks to change man's misconception about henosis, rather than his finite nature.