The Principle of Nightmares

During nightmares, the body cannot move and the mouth cannot make a sound—this is because the body has been controlled, the brain's supreme faculty (indriya) has been controlled; in some cases, it is the manas that has been controlled by ghosts.

When the body is controlled, it cannot move, or moves involuntarily—this is the manas of ghosts and spirits manipulating it. But the mind consciousness is very clear and lucid, and the manas can also know it.

When the manas is controlled, not only can the body not move, or moves involuntarily, but the mind consciousness's speech and thinking are also involuntary—manipulated by the manas of ghosts and spirits. The bodily, verbal, and mental actions are all involuntary, and the mind consciousness is mostly unaware of this. Once it becomes aware, if the manas has strength, it can break free from the restraint and regain autonomy.