This book excerpt originally appeared in the December 1999 issue of HIGH TIMES.

When Carl Sagan died of pneumonia in 1996 at age 62, he was one of the most famous scientists in the world. Not only had he popularized the study of astronomy and pioneered the importance of searching for intelligent life on other planets, Sagan was one of our strongest voices for the responsible use of science. Almost single-handedly, he strove to dismiss the myth America could survive a nuclear war. He became the leading critic of Ronald Reagan's Star Wars defense plan. What nobody realized, however, is for most of his adult life, Sagan was a secret and avid pothead. Not only did he enjoy partaking of the sacred herb, he believed it provided him with creative and scientific insights.

For young people of the 1960s and 1970s, marijuana use was a rite of passage. To the young, smoking the illegal drug was the boldest way to rebel against parental and governmental authority. The term "groves of academe" took on a new meaning in universities, where the spiky-leaved plants grew vigorously and covertly under ultraviolet lamps in dormitory closets.

But many adults used "weed," too. Astronomer Carl Sagan had been a regular marijuana user from the early 1960s on. He believe the drug enhanced his creativity and insights. His closest friend of three decades, Harvard psychiatry professor Dr. Lester Grinspoon, a leading advocate of the decriminalization of marijuana, recalls an incident in the 1980s when one of his California admirers mailed him, unsolicited, some unusually high-quality pot. Grinspoon shared the joints with Sagan and his wife, Annie. Afterwards, Grinspoon recalls, Sagan asked if he could have the last joint because he had so much work to do the next day and that it would really help.

Grinspoon's 1971 book, Marijuana Reconsidered, included a long essay by the unidentified "Mr. X," who described his happy experiences with the drug. The essay identified Mr. X as a "professor at one of the top-ranking American universities" but disguised his identity by saying he was in his "early forties." In my 1999 interview with Grinspoon, he revealed that Mr. X was Sagan (who turned 37 the year the book was published by Harvard University Press). To Grinspoon, Sagan's use of the drug is dramatic disproof of the popular wisdom that pot diminishes motivation: "He was certainly highly motivated to work, to contribute."

Mr. X's essay is of interest not merely because it reveals Sagan's use of an illegal drug, but because it also offers a glimpse of feelings he rarely shared. Portions of the account follow:

It all began about 10 years ago. I had reached a considerably more relaxed period in my life — a time when I had come to feel that there was more to living than science, a time of awakening of my social consciousness and amiability, a time when I was open to new experiences. I had become friendly with a group of people who occasionally smoked cannabis, irregularly, but with evident pleasure. Initially, I was unwilling to participate, but the apparent euphoria that cannabis produced and the fact that there was no physiological addiction to the plant eventually persuaded me to try. My initial experiences were entirely disappointing: there was no effect at all, and I began to entertain a variety of hypotheses about cannabis being a placebo which worked by expectation and hyperventilation rather than by chemistry. After about five or six unsuccessful attempts, however, it happened. I was lying on my back in a friend's living room idly examining the pattern of shadows on the ceiling cast by a potted plant (not cannabis!). I suddenly realized that I was examining an intricately detailed miniature Volkswagen, distinctly outlined by the shadows. I was very skeptical at this perception, and tried to find inconsistencies between Volkwagens and what I viewed on the ceiling. But it was all there, down to the hubcaps, license plate, chrome and even the small handle used for opening the trunk. When I closed my eyes, I was stunned to find that there was a movie going on on the inside of my eyelids. Flash… a simple country scene with red farmhouse, blue sky, white clouds, yellow path meandering over green hills to the horizon. Flash… same scene, orange house, brown sky, red clouds, yellow path, violet fields… Flash, Flash, Flash. The flashes came to me about once a heartbeat.

"I smile, or sometimes even laugh out loud at the pictures on the insides of my eyelids." Mr. X/Sagan wrote. Even so, he remained the astute scientific observer:

While my early perceptions were all visual, and curiously lacking in images of human beings, both of these items have changed over the intervening years… I test whether I'm high by closing my eyes and looking for the flashes. They come long before there are any alterations in my visual or other perceptions. I would guess that this is a signal-to-noise problem, the visual noise level being very low with my eyes closed. Another interesting information-theoretical aspect is the outlines of figures, caricatures, not photographs. I think this is simply a matter of information compression: it would be impossible to grasp the total content of an image with the information content of an ordinary photograph, say 108 bits, in the fraction of a second which a flash occupies.

"I find that today a single joint is enough to get me high… in one movie theater recently I found I could get high just by inhaling the cannabis smoke which permeated the theater." Pot enhanced his pleasure in music and food ("A potato will have the texture, body, and taste like that of other potatoes, but much more so."). Sex, too: marijuana "gives an exquisite sensitivity, but on the other hand it postpones orgasm, in part by distracting me with the profusion of images passing before my eyes."

The drug also "greatly improved my appreciation for art, a subject which I had never much appreciated before." During a high, he said:

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… There is a myth about such highs: The user has an illusion of great insight, but does not survive scrutiny in the morning. I am convinced that is an error, and that the devastating insights achieved when high are real insights: the main problem is putting these insights in a form acceptable to the quite different self that we are when we're down the next day. Some of the hardest work I've ever done has been put to such insights down on tape or in writing. The problem is that 10 even more interesting ideas or images have to be lost in the effort of recording one."

From such insights, he drew political inspiration:

I find that most of the insights I achieve when high are into social issues… I can remember one occasion, taking a shower with my wife while high, in which I had an idea on the origins and invalidities of racism in terms of Gaussian distribution curves. It was a point obvious in a way, but rarely talked about. I drew the curves in soap on the shower wall, and went to write the idea down. One idea led to another, and at the end of about an hour of extremely hard work, I found I had written 11 short essays on a wide range of social, political, philosophical, and human biological topics… I have used them in university commencement addresses, public lectures and in my books.

Sagan added: "I have on a few occasions been forced to drive in heavy traffic when I'm high. I've negotiated it with no difficulty at all, although I did have some thoughts about the marvelous cherry-red color of traffic lights."

Did pot enhance Sagan's scientific work? "I have made a conscious effort to think of a few particularly difficult current problems in my field when high," wrote Mr X. "It works, at least to a degree." While stoned, he thought of a "very bizarre possibility" that might reconcile certain disparate facts, "one that I'm sure I would never have thought of [while] down. I've written a paper which mentions this idea in passing. I think it's very unlikely to be true, but it has consequences which are experimentally testable, which is the hallmark of an acceptable theory."

Excerpted from Carl Sagan, A Life; John Wiley & Sons, Inc.