Author Christopher Booker characterises this as the "dialectical three", where "the first is wrong in one way, the second in another or opposite way, and only the third, in the middle, is just right". Booker continues: "This idea that the way forward lies in finding an exact middle path between opposites is of extraordinary importance in storytelling".[24] This concept has spread across many other disciplines, particularly developmental psychology, biology, economics and engineering where it is called the "Goldilocks principle".[25][26] In planetary astronomy, a planet orbiting its sun at just the right distance for liquid water to exist on its surface, neither too hot nor too cold, is referred to as being in the 'Goldilocks Zone'.