Plotinos: Complete Works, v. 4 In Chronological Order,...

31. (1) When one being subsists by dependence on any other, and not by self-dependence and withdrawal from any other, it could not turn itself towards itself to know itself by separating from (the substrate) by which it subsists. By withdrawing from its own existence it would alter and perish. But when one being cognizes itself by withdrawal from that to which it is united, when it grasps itself as independent of that being, and succeeds in doing so without exposing itself to destruction, it evidently does not derive its "being" or nature from the being from which it can, without perishing, withdraw, to face itself, and know itself independently. If sight, and in general all sensation do not feel itself, nor perceive itself on separating from the body, and do not subsist by itself; if, on the contrary, intelligence think better by separating from the body, and can be converted to itself without perishing, evidently sense-faculties are actualized only by help of the body, while intelligence actualizes and exists by itself, and not by the body.