Start to feel paranoid. Marvel at the sense that "everything is connected". Annoy your mates because only you see the connections. Eruditely quote some medieval Arab poetry, to explain away the urge to satisfy the munchies with a quick run down to the Spar for 10 bags of crisps: "Stoned people pounce on sweets as greedily as lover on the mouth of his beloved" (Ibn al Kharrat, 1375-1436).
Then throw in a grand conspiracy theory that marijuana has been outlawed because hemp, the plant from which it comes, could save the world - thereby cutting the profits of multinational food, paper, drug and fuel manufacturers. You have become that entertaining phenomenon: the pro-cannabis activist. One such campaigner is Patrick Matthews, author of Cannabis Culture: A Journey Through Disputed Territory (Bloomsbury, £12.99). "Smokers tend to have a know-it-all quality, which I'm perhaps especially prone to." Originally a wine writer, Matthews won acclaim for his book, The Wild Bunch: Great Wines from Small Producers. He writes well when drinking wine. When smoking? Not quite. He claims that when he began to write Cannabis Culture, he was neutral about whether or not cannabis should be legalised.
Matthews lost his neutrality somewhere during field research in the Hotel Tidiguine in Ketama, a mountain village in Morocco synonymous with kif, Morocco's main export crop. He saw, he inhaled (deeply, several times) and he succumbed. "A chief attraction of cannabis is that everyone can puff on a spliff and discover the joys of deconstruction and analysis," he writes. "Governments don't like this stuff," we're assured, "because they don't like people thinking for themselves." This is al asar - `the secrets' - as described by medieval Turkish Sufis."
Hash devastated the medieval Arab world by turning everyone into passive pot-heads with no ambition, Matthews admits. In the developing world today, hash culture has convinced some people that Bob Marley is God, which should be enough to put you off.
"It is reasonable to be worried by the way cannabis blurs the distinction between pattern-recognition and pattern-making," writes Matthews. "But how much does it actually matter? No one should live their life under a burden of delusions, but a period without being stoned - which would seem a sensible idea in any case - should give time to undertake some quality control. At least pot rewards people for thinking, which is more than you can say for alcohol."
Despite such balderdash, cannabis campaigners are winning some converts with the news that cannabis has medical uses. Cannabis seems to provide genuine relief to multiple sclerosis (MS) sufferers, and a British House of Lords committee recommended that until cannabis-based drugs can be developed, MS sufferers should be allowed cannabis on prescription. Other conditions which cannabis may help include chronic pain, migraine, nausea induced by chemotherapy, glaucoma, depression, AIDS wasting syndrome and, surprisingly, asthma and emphysema.
In 1992, scientists discovered that THC, a cannabinoid and the key chemical in marijuana that communicates to brain cells, has a human equivalent. This they called anandamide, from "ananda" or "bliss" in Sanskrit, the language in which cannabis was first described as an aid to religious experience 3,000 years ago. Since then, new cannabinoids have been discovered. Eventually, synthetic cannabinoids may be developed as drugs to treat various conditions so that the patient has all the benefits of cannabis, without the unpleasant side-effects.
In other words, people who actually need cannabis to ease the symptoms of disease may be able to benefit, without turning into stoned pot-heads, which is good news.