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

4. While separating ourselves from existence we by thought beget nonentity (matter). While remaining united with existence, we also conceive of nonentity (the one). Consequently, when we separate ourselves from existence, we do not conceive of the nonentity which is above existence (the one), but we beget by thought something that is deceptive, and we put ourselves in the condition (of indetermination) in which one is when outside of oneself. Just as each one can really, and by himself, raise himself to the non-existence which is above existence (the One); so (by separating oneself from existence by thought), we may reach the nonentity beneath existence.