Simplify the following text for a Grade 10 native English-speaking person.
Original: Freud discussed this model in the 1920 essay Beyond the Pleasure Principle , and fully elaborated upon it in The Ego and the Id ( 1923 ) , in which he developed it as an alternative to his previous topographic schema ( i.e. , conscious , unconscious , and preconscious ) .
Simplified: Freud discussed this model in the 1920 essay Beyond the Pleasure Principle , and fully elaborated upon it in The Ego and the Id ( 1923 ) .