Together with a chap called Peter Schmidt he developed a game called Oblique Strategies, a series of cards with gnomic phrases printed on them, designed to encourage lateral thinking:
"These cards evolved from our separate observations of the principles underlying what we are doing. Sometimes they were recognized in retrospect (intellect catching up with intuition), sometimes they were identified as they were happening, sometimes they were formulated. They can be used as a pack (a set of posibilities being continuously reviewed in the mind) or by drawing a single card from a shuffled pack when a dilemma occurs in a working situation. In this case the card is trusted even if it appropriateness is quite unclear. They are not final, as new ideas will present themselves, and others will become self-evident."
Though aimed at musicians anyone who wants to partake in creative arts can use them. Here are some drawn at random (the way they're supposed to be drawn):
Courage!
Simply a matter of work
Remove ambiguities and convert to specifics
Go outside. Shut the door.
Spectrum analysis
Intentions -nobility of -humility of -credibility of
Not building a wall but making a brick
Make a sudden, destructive unpredictable action; incorporate
Repetition is a form of change
What is the reality of the situation?
Listen to the quiet voice
Take away the elements in order of apparent non-importance