ENEMUS

The following provides a quick look at Yeats's Faculty Psychology:

The Four Faculties

Characteristics

Will (The Is)

will, drive, natural ego

Mask (The Ought)

emotion, desire; what one wishes to become; what one reverences

Creative Mind (Thought, the Knower)

intellect; innate universal Ideas; the consciously constructive mind

Body of Fate (Object of Thought; the Known)

environment (both physical and mental)

The Four Faculties are the result of the four memories of the Daimon (daemon) or the Ultimate Self of the Man:

The Will (The Is) or the natural ego of man is shaped out of the Daimon's memory of all the events of his present life, whether consciously remembered or not.
The Mask (The Ought), the object of desire or idea of the good, is shaped out of the Daimon's memory of the momenta of exaltation in his past lives.
The Creative Mind (Thought, the Knower) is shaped out of the Daimon's memory of ideas--or universals--displayed by actual men in past lives or their spirits between lives.
The Body of Fate (Object of Thought; the Known) is the series of events forced upon him from without and is shaped out of the Daimon's memory of the events of his past incarnations.

The Four Principles are the powers that guide the Four Faculties and deal with life from death to birth: