Play

"There can be no play without rules." Paul Rand

"Dare to be naïve." 

Buckminster Fuller, Synergetics: Explorations in the Geometry of Thinking (1975)

Being playful (in the context of illustration or other artistic process) would seem to be based on the ability to be inventive, disengaging the rational mind and allowing the childlike, creative mind to spur itself onwards, like a self-propelling contraption. In this altered state, the mind can make leaps and connections which the rational mind may struggle with. By removing the "Why?" from the process, all things are possible. The meaning and language of symbols can become more fluid and perception of ideas can become more abstract. It's the rules of play which Paul Rand mentions which allow the actual creation of an artwork to occur. They allow a route out from this creative state into the real world.