The key to the shift has been the emphasis on marijuana’s medical properties. Human beings have used marijuana as medicine for millennia. It was once sold in the States by Eli Lilly, the pharmaceutical manufacturer. Allowing this compassionate use for a few soon revealed, accidentally, how harmless it is. It is not chemically addictive, although some mild withdrawal can happen if you are a regular pot-smoker and go cold turkey. Its side-effects are minimal compared with those of most authorised drugs for similar conditions. It is far less addictive than tobacco or alcohol. It leads to no measurable degree of antisocial behaviour, as is the case with, say, crystal meth or cocaine or heroin. Many of its users are successful, productive members of society who simply prefer it to alcohol as a relaxant in the evening or as a way to get through cancer treatment.