"There is no off position on the genius switch"

In this quote, David Letterman is suggesting that real genius is not something that can be turned on or off like a light switch. He is indicating that being a genius is a continuous state of being, instead of something that can be controlled or manipulated. This might be analyzed as a commentary on the natural nature of genius, recommending that it is not something that can be learned or gotten, but rather something that an individual is born with. It might likewise be seen as a funny way of stating that as soon as somebody is a genius, they can not just turn it off and go back to being "normal." Overall, this quote highlights the concept that genius is a special and unchangeable quality.