Edward de Bono Quote

Vertical thinking is selection by exclusion. One works within a frame of reference and throws out what is not relevant. With lateral thinking one realizes that a pattern cannot be restructured from within itself but only as the result of some outside influence. So one welcomes outside influences for their provocative action. The more irrelevant such influences are the more chance there is of altering the established pattern. To look only for things that are relevant means perpetuating the current pattern.

p. 32 as cited in: ACEEE (1994) 1994 ACEEE Summer Study on Energy Efficiency in Buildings. p. 165. - Lateral Thinking : Creativity Step by Step (1970)