David Hillman isn't the first classics scholar to have cited historical texts that suggest recreational drug use was common in antiquity, but doing so at the University of Wisconsin in 2004 almost cost him his degree. His doctoral thesis review committee objected to the idea that writers such as the Roman poet Ovid not only consumed drugs but used them to inspire their writing. The committee gave Hillman a choice: remove the drug references or kiss your Ph.D. goodbye. Hillman played ball and then turned around and wrote The Chemical Muse: Drug Use and the Roots of Western Civilization, which was published in July by Thomas Dunne Books, an imprint of Macmillan. Mike Riggs interviewed Hillman in December.

Q: Why don't we know more about the history of recreational drug use?

A: People haven't heard about it because we're living in a prohibitionist century. Sigmund Freud's cocaine use is a great example, because cocaine was widely consumed pre-prohibition through Coca-Cola, as a pick-me-up. This was also back when opium was a common drug, and people like [poets Samuel Taylor] Coleridge and [Charles] Baudelaire had no problem with it whatsoever. Even [Friedrich] Nietzsche, who was a brilliant classicist in his day, talks about the use of drugs in antiquity. So my argument is nothing new, but it's new to the last 100 years and the time of prohibition, when drug use was suddenly given a renewed moral stigma.

Q: How has Christianity changed our understanding of antiquity?

A: We can't help but look at these texts through the lens of Christianity. It's an artifact of history that we've come through Christianity and it's become a part of our culture. But there was no Christianity when these texts were written. Judeo-Christian culture is based upon a system of commandments, whereas the Greek culture was based on "the good is the beautiful, and the beautiful is good."

One thing I didn't mention in the book, or didn't push, is that there's no word for homosexuality in antiquity. The Greeks had no concept of homosexual, or queer, or gay. You couldn't be a sexual this or a sexual that, but you could put A into B, or play around with C and D at the same time, or hang X, Y, and Z from the ceiling. It's the same thing with the word junkie. The Greeks had no term for hophead or dopehead or stoner—or any of the negative terms that we have—yet all of their literature is saturated with drugs.

Q: What are some examples of classical drug use that we'd probably frown on today?

A: The Greeks used to give their infants raw, crude opium latex. Why would they do such a thing? You can find the answer in Greek medical texts: ear infections. When your infant is sick, the opium kills its pain and lets it sleep. In the case of diarrhea, the opium causes constipation, which means the child can retain water and get some sleep.

Q: At what point in Western history did drugs become taboo?

A: The oldest evidence for an anti-drug movement in Western culture can be found in the early Church fathers. With the rise of Christianity as a state-sanctioned religion, pagan drug users became active targets for discrimination and persecution. It's then that we begin to see the first instances of drug control. I keep asking myself, why is it that the Hippocratics and the ancient physicians and the ancient botanists and the ancient philosophers encourage and write about drug use, but all of a sudden, there's a problem?

When you read some of the late pagan literature, you see this battle going on between Christianity and paganism, but it's not a cyclical event; it's a battle for establishing traditions. In the earliest anti-drug texts we have, all of which are Christian, the Christian fathers are telling their congregations to stop using drugs because the ecstatic out-of-mind experiences associated with drugs were an integral part of non-Christian religious practice.