"Sometimes a kind of existential perception of the absurd comes over me and I see with awful certainty the hypocrisies and posturing of myself and my fellow men. And at other times, there is a different sense of the absurd, a playful and whimsical awareness. Both of these senses of the absurd can be communicated, and some of the most rewarding highs I've had have been in sharing talk and perceptions and humor. Cannabis brings us an awareness that we spend a lifetime being trained to overlook and forget and put out of our minds. A sense of what the world is really like can be maddening; cannabis has brought me some feelings for what it is like to be crazy, and how we use that word 'crazy' to avoid thinking about things that are too painful for us. In the Soviet Union political dissidents are routinely placed in insane asylums. The same kind of thing, a little more subtle perhaps, occurs here: 'did you hear what Lenny Bruce said yesterday? He must be crazy.' When high on cannabis I discovered that there's somebody inside in those people we call mad."
Carl Sagan, under the pseudonym "Mr X.," describing his experience with marijuana (from an essay in the book Reconsidering Marijuana).