Lyric discussion by QuintessOD 

Cover art for Pure Imagination lyrics by Willy Wonka and the Chocolate Factory

All very sweet and optimistic until a troublingly dark final verse.

"There is no life I know, To compare with pure imagination, Living there, you'll be free"

Writer is sorrowful at his inadequate life. Urges to give up, stop living there, and disappear into a dream-world. Only there will you be free of the prison of real life.

[Edit: clearer quote]

Negative
Subjective
Sadness
Escapism
Sorrow
Imagination
Struggle
Freedom