In 1926, thirteen years before James Webb Young’s Technique for Producing Ideas and more than three decades before Arthur Koestler’s seminal “bisociation” theory of how creativity works, Graham Wallas, sixty-eight at the time, penned The Art of Thought — an insightful theory outlining the four stages of the creative process, based both on his own empirical observations and on the accounts of famous inventors and polymaths.

Wallas outlines four stages of the creative process — preparation, incubation, illumination, and verification — dancing in a delicate osmosis of conscious and unconscious work.

In language adapted to the general reader as well as the student of psychology. It established itself as a standard guide to the mechanism of thought, and its message remains of essential value to a world confronted with problems of increasing complexity. 

Graham Wallas was an English socialist, social psychologist, educationalist, a leader of the Fabian Society and a co-founder of the London School of Economics.