Naturally, for a person who finds his identity in something other than his full organism is less than half a man. He is cut off from complete participation in nature. Instead of being a body, he 'has' a body. Instead of living and loving he 'has' instincts for survival and copulation.
Clay is molded to form a cup, But it is on its non-being that the utility of the cup depends. Doors and windows are cut out to make a room, But it is on its non-being that the utility of the room depends. Therefore turn being into advantage, and turn non-being into utility.