In The art of Thought (1926), Wallas elabora la celeberrima distinzione del processo creativo in quattro fasi: Preparazione, Incubazione, Illuminazione e Verifica.
Lavori
1889, Property under Socialism in Fabian Essays
1897, Life of Francis Place
1908, Human Nature in Politics
1914, The Great Society
1921, Our Social Heritage
1926, The art of Thought
1934, Social Judgement
1940, Men and Ideas, recueil d'articles avec une préface de Gilbert Murray